diff --git a/mobile/android/base/BrowserApp.java b/mobile/android/base/BrowserApp.java
index 40408a2829d..bf7fdbb8442 100644
--- a/mobile/android/base/BrowserApp.java
+++ b/mobile/android/base/BrowserApp.java
@@ -429,7 +429,7 @@ abstract public class BrowserApp extends GeckoApp
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
-        mAboutHomeStartupTimer = new Telemetry.Timer("FENNEC_STARTUP_TIME_ABOUTHOME");
+        mAboutHomeStartupTimer = new Telemetry.UptimeTimer("FENNEC_STARTUP_TIME_ABOUTHOME");
 
         final Intent intent = getIntent();
 
diff --git a/mobile/android/base/GeckoApp.java b/mobile/android/base/GeckoApp.java
index 83709caa1ef..ff5167d57b5 100644
--- a/mobile/android/base/GeckoApp.java
+++ b/mobile/android/base/GeckoApp.java
@@ -1153,8 +1153,8 @@ public abstract class GeckoApp
         }
 
         // The clock starts...now. Better hurry!
-        mJavaUiStartupTimer = new Telemetry.Timer("FENNEC_STARTUP_TIME_JAVAUI");
-        mGeckoReadyStartupTimer = new Telemetry.Timer("FENNEC_STARTUP_TIME_GECKOREADY");
+        mJavaUiStartupTimer = new Telemetry.UptimeTimer("FENNEC_STARTUP_TIME_JAVAUI");
+        mGeckoReadyStartupTimer = new Telemetry.UptimeTimer("FENNEC_STARTUP_TIME_GECKOREADY");
 
         Intent intent = getIntent();
         String args = intent.getStringExtra("args");
diff --git a/mobile/android/base/GeckoEvent.java b/mobile/android/base/GeckoEvent.java
index 0a6352f18f2..fa12547bba2 100644
--- a/mobile/android/base/GeckoEvent.java
+++ b/mobile/android/base/GeckoEvent.java
@@ -43,7 +43,7 @@ public class GeckoEvent {
     private static final String LOGTAG = "GeckoEvent";
 
     // Make sure to keep these values in sync with the enum in
-    // AndroidGeckoEvent in widget/android/AndroidJavaWrapper.h
+    // AndroidGeckoEvent in widget/android/AndroidJavaWrappers.h
     @JNITarget
     private enum NativeGeckoEvent {
         NATIVE_POKE(0),
@@ -76,13 +76,16 @@ public class GeckoEvent {
         TELEMETRY_HISTOGRAM_ADD(37),
         PREFERENCES_OBSERVE(39),
         PREFERENCES_GET(40),
-        PREFERENCES_REMOVE_OBSERVERS(41);
+        PREFERENCES_REMOVE_OBSERVERS(41),
+        TELEMETRY_UI_SESSION_START(42),
+        TELEMETRY_UI_SESSION_STOP(43),
+        TELEMETRY_UI_EVENT(44);
 
         public final int value;
 
         private NativeGeckoEvent(int value) {
             this.value = value;
-         }
+        }
     }
 
     /**
@@ -747,6 +750,30 @@ public class GeckoEvent {
         return event;
     }
 
+    public static GeckoEvent createTelemetryUISessionStartEvent(String session, long timestamp) {
+        GeckoEvent event = new GeckoEvent(NativeGeckoEvent.TELEMETRY_UI_SESSION_START);
+        event.mCharacters = session;
+        event.mTime = timestamp;
+        return event;
+    }
+
+    public static GeckoEvent createTelemetryUISessionStopEvent(String session, String reason, long timestamp) {
+        GeckoEvent event = new GeckoEvent(NativeGeckoEvent.TELEMETRY_UI_SESSION_STOP);
+        event.mCharacters = session;
+        event.mCharactersExtra = reason;
+        event.mTime = timestamp;
+        return event;
+    }
+
+    public static GeckoEvent createTelemetryUIEvent(String action, String method, long timestamp, String extras) {
+        GeckoEvent event = new GeckoEvent(NativeGeckoEvent.TELEMETRY_UI_EVENT);
+        event.mData = action;
+        event.mCharacters = method;
+        event.mCharactersExtra = extras;
+        event.mTime = timestamp;
+        return event;
+    }
+
     public void setAckNeeded(boolean ackNeeded) {
         mAckNeeded = ackNeeded;
     }
diff --git a/mobile/android/base/Telemetry.java b/mobile/android/base/Telemetry.java
index 284fa2e4f5d..bd5cf7354f6 100644
--- a/mobile/android/base/Telemetry.java
+++ b/mobile/android/base/Telemetry.java
@@ -5,31 +5,52 @@
 
 package org.mozilla.gecko;
 
+import org.mozilla.gecko.mozglue.RobocopTarget;
+
 import android.os.SystemClock;
 import android.util.Log;
 
+/**
+ * All telemetry times are relative to one of two clocks:
+ * 
+ * * Real time since the device was booted, including deep sleep. Use this
+ *   as a substitute for wall clock.
+ * * Uptime since the device was booted, excluding deep sleep. Use this to
+ *   avoid timing a user activity when their phone is in their pocket!
+ *
+ * The majority of methods in this class are defined in terms of real time.
+ */
+@RobocopTarget
 public class Telemetry {
     private static final String LOGTAG = "Telemetry";
 
+    public static long uptime() {
+        return SystemClock.uptimeMillis();
+    }
+
+    public static long realtime() {
+        return SystemClock.elapsedRealtime();
+    }
+
     // Define new histograms in:
     // toolkit/components/telemetry/Histograms.json
-    public static void HistogramAdd(String name,
-                                    int value) {
-        GeckoEvent event =
-            GeckoEvent.createTelemetryHistogramAddEvent(name, value);
+    public static void HistogramAdd(String name, int value) {
+        GeckoEvent event = GeckoEvent.createTelemetryHistogramAddEvent(name, value);
         GeckoAppShell.sendEventToGecko(event);
     }
 
-    public static class Timer {
-        private long mStartTime;
-        private String mName;
-        private boolean mHasFinished;
+    public abstract static class Timer {
+        private final long mStartTime;
+        private final String mName;
+
+        private volatile boolean mHasFinished = false;
         private volatile long mElapsed = -1;
 
+        protected abstract long now();
+
         public Timer(String name) {
             mName = name;
-            mStartTime = SystemClock.uptimeMillis();
-            mHasFinished = false;
+            mStartTime = now();
         }
 
         public void cancel() {
@@ -44,17 +65,76 @@ public class Telemetry {
             // Only the first stop counts.
             if (mHasFinished) {
                 return;
-            } else {
-                mHasFinished = true;
             }
 
-            final long elapsed = SystemClock.uptimeMillis() - mStartTime;
-            mElapsed = elapsed;
-            if (elapsed < Integer.MAX_VALUE) {
-                HistogramAdd(mName, (int)(elapsed));
-            } else {
-                Log.e(LOGTAG, "Duration of " + elapsed + " ms is too long to add to histogram.");
+            mHasFinished = true;
+
+            final long elapsed = now() - mStartTime;
+            if (elapsed < 0) {
+                Log.e(LOGTAG, "Current time less than start time -- clock shenanigans?");
+                return;
             }
+
+            mElapsed = elapsed;
+            if (elapsed > Integer.MAX_VALUE) {
+                Log.e(LOGTAG, "Duration of " + elapsed + "ms is too great to add to histogram.");
+                return;
+            }
+
+            HistogramAdd(mName, (int)(elapsed));
         }
     }
+
+    public static class RealtimeTimer extends Timer {
+        public RealtimeTimer(String name) {
+            super(name);
+        }
+
+        @Override
+        protected long now() {
+            return Telemetry.realtime();
+        }
+    }
+
+    public static class UptimeTimer extends Timer {
+        public UptimeTimer(String name) {
+            super(name);
+        }
+
+        @Override
+        protected long now() {
+            return Telemetry.uptime();
+        }
+    }
+
+    public static void startUISession(String sessionName) {
+        GeckoEvent event = GeckoEvent.createTelemetryUISessionStartEvent(sessionName, realtime());
+        GeckoAppShell.sendEventToGecko(event);
+    }
+
+    public static void stopUISession(String sessionName, String reason) {
+        GeckoEvent event = GeckoEvent.createTelemetryUISessionStopEvent(sessionName, reason, realtime());
+        GeckoAppShell.sendEventToGecko(event);
+    }
+
+    public static void sendUIEvent(String action, String method, long timestamp, String extras) {
+        GeckoEvent event = GeckoEvent.createTelemetryUIEvent(action, method, timestamp, extras);
+        GeckoAppShell.sendEventToGecko(event);
+    }
+
+    public static void sendUIEvent(String action, String method, long timestamp) {
+        sendUIEvent(action, method, timestamp, null);
+    }
+
+    public static void sendUIEvent(String action, String method, String extras) {
+        sendUIEvent(action, method, realtime(), extras);
+    }
+
+    public static void sendUIEvent(String action, String method) {
+        sendUIEvent(action, method, realtime(), null);
+    }
+
+    public static void sendUIEvent(String action) {
+        sendUIEvent(action, null, realtime(), null);
+    }
 }
diff --git a/mobile/android/base/tests/robocop.ini b/mobile/android/base/tests/robocop.ini
index 58112b02e5d..6169d5433ea 100644
--- a/mobile/android/base/tests/robocop.ini
+++ b/mobile/android/base/tests/robocop.ini
@@ -16,7 +16,6 @@ skip-if = processor == "x86"
 [testBrowserProvider]
 [testBrowserSearchVisibility]
 [testClearPrivateData]
-[testDeviceSearchEngine]
 [testDistribution]
 [testDoorHanger]
 [testFindInPage]
@@ -32,14 +31,11 @@ skip-if = processor == "x86"
 skip-if = processor == "x86"
 [testInputUrlBar]
 [testJarReader]
-[testJNI]
 [testLinkContextMenu]
 [testLoad]
 [testMailToContextMenu]
 [testMasterPassword]
-# [testMozPay] # see bug 945675
 [testNewTab]
-[testOrderedBroadcast]
 [testOverscroll]
 [testPanCorrectness]
 # disabled on x86 only; bug 927476
@@ -58,7 +54,6 @@ skip-if = processor == "x86"
 [testSessionOOMSave]
 [testSessionOOMRestore]
 [testSettingsMenuItems]
-[testSharedPreferences]
 # [testShareLink] # see bug 915897
 [testSystemPages]
 # disabled on x86 only; bug 907383
@@ -66,6 +61,13 @@ skip-if = processor == "x86"
 # [testThumbnails] # see bug 813107
 # [testVkbOverlap] # see bug 907274
 
+# Using JavascriptTest
+[testDeviceSearchEngine]
+[testJNI]
+# [testMozPay] # see bug 945675
+[testOrderedBroadcast]
+[testSharedPreferences]
+[testUITelemetry]
 
 # Used for Talos, please don't use in mochitest
 #[testPan]
diff --git a/mobile/android/base/tests/testUITelemetry.java b/mobile/android/base/tests/testUITelemetry.java
new file mode 100644
index 00000000000..a6f180df6ef
--- /dev/null
+++ b/mobile/android/base/tests/testUITelemetry.java
@@ -0,0 +1,38 @@
+package org.mozilla.gecko.tests;
+
+import org.mozilla.gecko.Telemetry;
+
+import android.util.Log;
+
+public class testUITelemetry extends JavascriptTest {
+    public testUITelemetry() {
+        super("testUITelemetry.js");
+    }
+
+    @Override
+    public void testJavascript() throws Exception {
+        blockForGeckoReady();
+        Log.i("GeckoTest", "Adding telemetry events.");
+
+        try {
+            Telemetry.sendUIEvent("enone", "method0");
+            Telemetry.startUISession("foo");
+            Telemetry.sendUIEvent("efoo", "method1");
+            Telemetry.startUISession("foo");
+            Telemetry.sendUIEvent("efoo", "method2");
+            Telemetry.startUISession("bar");
+            Telemetry.sendUIEvent("efoobar", "method3", "foobarextras");
+            Telemetry.stopUISession("foo", "reasonfoo");
+            Telemetry.sendUIEvent("ebar", "method4", "barextras");
+            Telemetry.stopUISession("bar", "reasonbar");
+            Telemetry.stopUISession("bar", "reasonbar2");
+            Telemetry.sendUIEvent("enone", "method5");
+        } catch (Exception e) {
+            Log.e("GeckoTest", "Oops.", e);
+        }
+
+        Log.i("GeckoTest", "Running remaining JS test code.");
+        super.testJavascript();
+    }
+}
+
diff --git a/mobile/android/base/tests/testUITelemetry.js b/mobile/android/base/tests/testUITelemetry.js
new file mode 100644
index 00000000000..0407314bb2d
--- /dev/null
+++ b/mobile/android/base/tests/testUITelemetry.js
@@ -0,0 +1,63 @@
+// -*- Mode: js2; tab-width: 2; indent-tabs-mode: nil; js2-basic-offset: 2; js2-skip-preprocessor-directives: t; -*-
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+Components.utils.import("resource://gre/modules/Services.jsm");
+
+function do_check_array_eq(a1, a2) {
+  do_check_eq(a1.length, a2.length);
+  for (let i = 0; i < a1.length; ++i) {
+    do_check_eq(a1[i], a2[i]);
+  }
+}
+
+add_test(function test_telemetry_events() {
+  let bridge = Components.classes["@mozilla.org/android/bridge;1"]
+                         .getService(Components.interfaces.nsIAndroidBridge);
+  let obsXPCOM = bridge.browserApp.getUITelemetryObserver();
+  do_check_true(!!obsXPCOM);
+
+  let obs = obsXPCOM.wrappedJSObject;
+  do_check_true(!!obs);
+
+  let measurements = obs.getUIMeasurements();
+
+  let expected = [
+    ["event", "enone", "method0", [], null],
+    ["event", "efoo", "method1", ["foo"], null],
+    ["event", "efoo", "method2", ["foo"], null],
+    ["event", "efoobar", "method3", ["foo", "bar"], "foobarextras"],
+    ["session", "foo", "reasonfoo"],
+    ["event", "ebar", "method4", ["bar"], "barextras"],
+    ["session", "bar", "reasonbar"],
+    ["event", "enone", "method5", [], null],
+  ];
+
+  do_check_eq(expected.length, measurements.length);
+
+  for (let i = 0; i < measurements.length; ++i) {
+    let m = measurements[i];
+
+    let type = m[0];
+    if (type == "event") {
+      let [type, action, method, sessions, extras] = expected[i];
+      do_check_eq(m.action, action);
+      do_check_eq(m.method, method);
+      do_check_array_eq(m.sessions, sessions);
+      do_check_eq(m.extras, extras);
+      continue;
+    }
+
+    if (type == "session") {
+      let [type, name, reason] = expected[i];
+      do_check_eq(m.name, name);
+      do_check_eq(m.reason, method);
+      continue;
+    }
+  }
+
+  run_next_test();
+});
+
+run_next_test();
diff --git a/mobile/android/chrome/content/browser.js b/mobile/android/chrome/content/browser.js
index f4436f45907..5c3e7e66a36 100644
--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -338,7 +338,6 @@ var BrowserApp = {
     DesktopUserAgent.init();
     Distribution.init();
     Tabs.init();
-    UITelemetry.init();
 #ifdef ACCESSIBILITY
     AccessFu.attach(window);
 #endif
@@ -1530,6 +1529,10 @@ var BrowserApp = {
     return this.getTabForId(tabId);
   },
 
+  getUITelemetryObserver: function() {
+    return UITelemetry;
+  },
+
   getPreferences: function getPreferences(requestId, prefNames, count) {
     this.handlePreferencesRequest(requestId, prefNames, false);
   },
diff --git a/toolkit/components/telemetry/UITelemetry.jsm b/toolkit/components/telemetry/UITelemetry.jsm
index c8720f0b2d6..e7aa8838740 100644
--- a/toolkit/components/telemetry/UITelemetry.jsm
+++ b/toolkit/components/telemetry/UITelemetry.jsm
@@ -7,80 +7,78 @@
 const Cu = Components.utils;
 
 this.EXPORTED_SYMBOLS = [
-  "UITelemetry"
+  "UITelemetry",
 ];
 
 Cu.import("resource://gre/modules/Services.jsm");
 
 /**
  * UITelemetry is a helper JSM used to record UI specific telemetry events.
+ *
+ * It implements nsIUITelemetryObserver, defined in nsIAndroidBridge.idl.
  */
-this.UITelemetry =  {
+this.UITelemetry = Object.freeze({
+  _activeSessions: {},
+  _measurements: [],
 
-  measurements: [],
-
-  init: function init() {
-    Services.obs.addObserver(this, "UITelemetry:Event", false);
-    Services.obs.addObserver(this, "UITelemetry:Session", false);
-  },
-
-  observe: function observe(aMessage, aTopic, aData) {
-    switch(aTopic) {
-      case "UITelemetry:Event":
-        let args = JSON.parse(aData);
-        this.addEvent(args.action, args.method, args.extras, args.timestamp);
-        break;
-      case "UITelemetry:Session":
-        args = JSON.parse(aData);
-        let sessionName = args.name;
-        let timestamp = args.timestamp;
-        if (args.state == "start") {
-          this.startSession(sessionName, timestamp);
-        } else if (args.state == "stop") {
-          this.stopSession(sessionName, timestamp);
-        }
-        break;
-    }
+  /**
+   * This exists exclusively for testing -- our events are not intended to
+   * be retrieved via an XPCOM interface.
+   */
+  get wrappedJSObject() {
+    return this;
   },
 
   /**
-   * Adds a single event described by an action, and the calling method. Optional
-   * paramaters are extras and timestamp. The timestamp will be set here if it is
-   * not passed in by the caller.
+   * Holds the functions that provide UITelemetry's simple
+   * measurements. Those functions are mapped to unique names,
+   * and should be registered with addSimpleMeasureFunction.
    */
-  addEvent: function addEvent(aAction, aMethod, aExtras, aTimestamp) {
-    let timestamp = aTimestamp || Date.now();
+  _simpleMeasureFunctions: {},
+
+  /**
+   * Adds a single event described by a timestamp, an action, and the calling
+   * method.
+   *
+   * Optionally provide a string 'extras', which will be recorded as part of
+   * the event.
+   *
+   * All extant sessions will be recorded by name for each event.
+   */
+  addEvent: function(aAction, aMethod, aTimestamp, aExtras) {
+    let sessions = Object.keys(this._activeSessions);
     let aEvent = {
       type: "event",
       action: aAction,
       method: aMethod,
-      timestamp: timestamp
+      sessions: sessions,
+      timestamp: aTimestamp,
     };
 
-    if (aExtras) aEvent.extras = aExtras;
-    this._logEvent(aEvent);
-  },
+    if (aExtras) {
+      aEvent.extras = aExtras;
+    }
 
-  activeSessions: {},
+    this._recordEvent(aEvent);
+  },
 
   /**
    * Begins tracking a session by storing a timestamp for session start.
    */
-  startSession: function startSession(aName, aTimestamp) {
-   let timestamp = aTimestamp || Date.now();
-   if (this.activeSessions[aName]) {
-    // Do not overwrite a previous event start if it already exsts.
-    return;
-   }
-   this.activeSessions[aName] = timestamp;
+  startSession: function(aName, aTimestamp) {
+    if (this._activeSessions[aName]) {
+      // Do not overwrite a previous event start if it already exists.
+      return;
+    }
+    this._activeSessions[aName] = aTimestamp;
   },
 
   /**
    * Tracks the end of a session with a timestamp.
    */
-  stopSession: function stopSession(aName, aTimestamp) {
-    let timestamp = aTimestamp || Date.now();
-    let sessionStart = this.activeSessions[aName];
+  stopSession: function(aName, aReason, aTimestamp) {
+    let sessionStart = this._activeSessions[aName];
+    delete this._activeSessions[aName];
 
     if (!sessionStart) {
       Services.console.logStringMessage("UITelemetry error: no session [" + aName + "] to stop!");
@@ -90,24 +88,18 @@ this.UITelemetry =  {
     let aEvent = {
       type: "session",
       name: aName,
+      reason: aReason,
       start: sessionStart,
-      end: timestamp
+      end: aTimestamp,
     };
 
-    this._logEvent(aEvent);
+    this._recordEvent(aEvent);
   },
 
-  _logEvent: function sendEvent(aEvent) {
-    this.measurements.push(aEvent);
+  _recordEvent: function(aEvent) {
+    this._measurements.push(aEvent);
   },
 
-  /**
-   * Holds the functions that provide UITelemety's simple
-   * measurements. Those functions are mapped to unique names,
-   * and should be registered with addSimpleMeasureFunction.
-   */
-  _simpleMeasureFuncs: {},
-
   /**
    * Called by TelemetryPing to populate the simple measurement
    * blob. This function will iterate over all functions added
@@ -116,8 +108,8 @@ this.UITelemetry =  {
    */
   getSimpleMeasures: function() {
     let result = {};
-    for (let name in this._simpleMeasureFuncs) {
-      result[name] = this._simpleMeasureFuncs[name]();
+    for (let name in this._simpleMeasureFunctions) {
+      result[name] = this._simpleMeasureFunctions[name]();
     }
     return result;
   },
@@ -132,22 +124,22 @@ this.UITelemetry =  {
    * registered for it.
    */
   addSimpleMeasureFunction: function(aName, aFunction) {
-    if (aName in this._simpleMeasureFuncs) {
-      throw new Error("A simple measurement function is already registered for "
-                      + aName);
-    }
-    if (!aFunction || typeof aFunction !== 'function') {
-      throw new Error("A function must be passed as the second argument.");
+    if (aName in this._simpleMeasureFunctions) {
+      throw new Error("A simple measurement function is already registered for " + aName);
     }
 
-    this._simpleMeasureFuncs[aName] = aFunction;
+    if (!aFunction || typeof aFunction !== 'function') {
+      throw new Error("addSimpleMeasureFunction called with non-function argument.");
+    }
+
+    this._simpleMeasureFunctions[aName] = aFunction;
   },
 
   removeSimpleMeasureFunction: function(aName) {
-    delete this._simpleMeasureFuncs[aName];
+    delete this._simpleMeasureFunctions[aName];
   },
 
   getUIMeasurements: function getUIMeasurements() {
-    return this.measurements.slice();
+    return this._measurements.slice();
   }
-};
+});
diff --git a/widget/android/AndroidJavaWrappers.cpp b/widget/android/AndroidJavaWrappers.cpp
index e984ea2be79..21ccb490de9 100644
--- a/widget/android/AndroidJavaWrappers.cpp
+++ b/widget/android/AndroidJavaWrappers.cpp
@@ -564,6 +564,27 @@ AndroidGeckoEvent::Init(JNIEnv *jenv, jobject jobj)
             break;
         }
 
+        case TELEMETRY_UI_SESSION_START: {
+            ReadCharactersField(jenv);
+            mTime = jenv->GetLongField(jobj, jTimeField);
+            break;
+        }
+
+        case TELEMETRY_UI_SESSION_STOP: {
+            ReadCharactersField(jenv);
+            ReadCharactersExtraField(jenv);
+            mTime = jenv->GetLongField(jobj, jTimeField);
+            break;
+        }
+
+        case TELEMETRY_UI_EVENT: {
+            ReadCharactersField(jenv);
+            ReadCharactersExtraField(jenv);
+            ReadDataField(jenv);
+            mTime = jenv->GetLongField(jobj, jTimeField);
+            break;
+        }
+
         case PREFERENCES_OBSERVE:
         case PREFERENCES_GET: {
             ReadStringArray(mPrefNames, jenv, jPrefNamesField);
diff --git a/widget/android/AndroidJavaWrappers.h b/widget/android/AndroidJavaWrappers.h
index f0f26c6030f..19977cc7667 100644
--- a/widget/android/AndroidJavaWrappers.h
+++ b/widget/android/AndroidJavaWrappers.h
@@ -686,11 +686,14 @@ public:
         PREFERENCES_OBSERVE = 39,
         PREFERENCES_GET = 40,
         PREFERENCES_REMOVE_OBSERVERS = 41,
+        TELEMETRY_UI_SESSION_START = 42,
+        TELEMETRY_UI_SESSION_STOP = 43,
+        TELEMETRY_UI_EVENT = 44,
         dummy_java_enum_list_end
     };
 
     enum {
-        // Memory pressue levels, keep in sync with those in MemoryMonitor.java
+        // Memory pressure levels. Keep these in sync with those in MemoryMonitor.java.
         MEMORY_PRESSURE_NONE = 0,
         MEMORY_PRESSURE_CLEANUP = 1,
         MEMORY_PRESSURE_LOW = 2,
diff --git a/widget/android/nsAppShell.cpp b/widget/android/nsAppShell.cpp
index 98b77f712ef..f6a9e13b972 100644
--- a/widget/android/nsAppShell.cpp
+++ b/widget/android/nsAppShell.cpp
@@ -259,8 +259,7 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
         NativeEventCallback();
         break;
 
-    case AndroidGeckoEvent::SENSOR_EVENT:
-      {
+    case AndroidGeckoEvent::SENSOR_EVENT: {
         InfallibleTArray<float> values;
         mozilla::hal::SensorType type = (mozilla::hal::SensorType) curEvent->Flags();
 
@@ -371,7 +370,6 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
 
     case AndroidGeckoEvent::VIEWPORT:
     case AndroidGeckoEvent::BROADCAST: {
-
         if (curEvent->Characters().Length() == 0)
             break;
 
@@ -385,6 +383,57 @@ nsAppShell::ProcessNextNativeEvent(bool mayWait)
         break;
     }
 
+    case AndroidGeckoEvent::TELEMETRY_UI_SESSION_STOP: {
+        if (curEvent->Characters().Length() == 0)
+            break;
+
+        nsCOMPtr<nsIUITelemetryObserver> obs;
+        mBrowserApp->GetUITelemetryObserver(getter_AddRefs(obs));
+        if (!obs)
+            break;
+
+        obs->StopSession(
+                nsString(curEvent->Characters()).get(),
+                nsString(curEvent->CharactersExtra()).get(),
+                curEvent->Time()
+                );
+        break;
+    }
+
+    case AndroidGeckoEvent::TELEMETRY_UI_SESSION_START: {
+        if (curEvent->Characters().Length() == 0)
+            break;
+
+        nsCOMPtr<nsIUITelemetryObserver> obs;
+        mBrowserApp->GetUITelemetryObserver(getter_AddRefs(obs));
+        if (!obs)
+            break;
+
+        obs->StartSession(
+                nsString(curEvent->Characters()).get(),
+                curEvent->Time()
+                );
+        break;
+    }
+
+    case AndroidGeckoEvent::TELEMETRY_UI_EVENT: {
+        if (curEvent->Characters().Length() == 0)
+            break;
+
+        nsCOMPtr<nsIUITelemetryObserver> obs;
+        mBrowserApp->GetUITelemetryObserver(getter_AddRefs(obs));
+        if (!obs)
+            break;
+
+        obs->AddEvent(
+                nsString(curEvent->Data()).get(),
+                nsString(curEvent->Characters()).get(),
+                curEvent->Time(),
+                nsString(curEvent->CharactersExtra()).get()
+                );
+        break;
+    }
+
     case AndroidGeckoEvent::LOAD_URI: {
         nsCOMPtr<nsICommandLineRunner> cmdline
             (do_CreateInstance("@mozilla.org/toolkit/command-line;1"));
diff --git a/widget/android/nsIAndroidBridge.idl b/widget/android/nsIAndroidBridge.idl
index e214391373c..5f04aff0116 100644
--- a/widget/android/nsIAndroidBridge.idl
+++ b/widget/android/nsIAndroidBridge.idl
@@ -11,7 +11,20 @@ interface nsIBrowserTab : nsISupports {
   readonly attribute float scale;
 };
 
-[scriptable, uuid(7508b826-4129-40a0-91da-2a6bba33681f)]
+[scriptable, uuid(08426a73-e70b-4680-9282-630932e2b2bb)]
+interface nsIUITelemetryObserver : nsISupports {
+  void startSession(in wstring name,
+                    in unsigned long timestamp);
+  void stopSession(in wstring name,
+                   in wstring reason,
+                   in unsigned long timestamp);
+  void addEvent(in wstring action,
+                in wstring method,
+                in unsigned long timestamp,
+                in wstring extras);
+};
+
+[scriptable, uuid(c31331d2-afad-460f-9c66-728b8c838cec)]
 interface nsIAndroidBrowserApp : nsISupports {
   nsIBrowserTab getBrowserTab(in int32_t tabId);
   void getPreferences(in int32_t requestId,
@@ -21,7 +34,9 @@ interface nsIAndroidBrowserApp : nsISupports {
                           [array, size_is(count)] in wstring prefNames,
                           in unsigned long count);
   void removePreferenceObservers(in int32_t requestId);
+  nsIUITelemetryObserver getUITelemetryObserver();
 };
+
 [scriptable, uuid(59cfcb35-69b7-47b2-8155-32b193272666)]
 interface nsIAndroidViewport : nsISupports {
   readonly attribute float x;