diff --git a/dom/plugins/base/nsNPAPIPlugin.cpp b/dom/plugins/base/nsNPAPIPlugin.cpp
index 8923e0b6dc9..bacd13e03e8 100644
--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -54,7 +54,6 @@
 #include "nsNPAPIPluginStreamListener.h"
 #include "nsIServiceManager.h"
 #include "nsThreadUtils.h"
-#include "nsIPrivateBrowsingService.h"
 #include "mozilla/Preferences.h"
 
 #include "nsIPluginStreamListener.h"
@@ -105,6 +104,8 @@
 #include "nsJSNPRuntime.h"
 #include "nsIHttpAuthManager.h"
 #include "nsICookieService.h"
+#include "nsILoadContext.h"
+#include "nsIDocShell.h"
 
 #include "nsNetUtil.h"
 
@@ -2135,11 +2136,12 @@ _getvalue(NPP npp, NPNVariable variable, void *result)
   }
 
   case NPNVprivateModeBool: {
-    nsCOMPtr<nsIPrivateBrowsingService> pbs = do_GetService(NS_PRIVATE_BROWSING_SERVICE_CONTRACTID);
-    if (pbs) {
-      bool enabled;
-      pbs->GetPrivateBrowsingEnabled(&enabled);
-      *(NPBool*)result = (NPBool)enabled;
+    nsCOMPtr<nsIDocument> doc = GetDocumentFromNPP(npp);
+    nsCOMPtr<nsPIDOMWindow> domwindow = do_QueryInterface(doc);
+    if (domwindow) {
+      nsCOMPtr<nsIDocShell> docShell = domwindow->GetDocShell();
+      nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(docShell);
+      *(NPBool*)result = (NPBool)(loadContext && loadContext->UsePrivateBrowsing());
       return NPERR_NO_ERROR;
     }
     return NPERR_GENERIC_ERROR;
diff --git a/dom/plugins/base/nsNPAPIPluginInstance.cpp b/dom/plugins/base/nsNPAPIPluginInstance.cpp
index 4d5f091284b..6400042c72d 100644
--- a/dom/plugins/base/nsNPAPIPluginInstance.cpp
+++ b/dom/plugins/base/nsNPAPIPluginInstance.cpp
@@ -48,7 +48,6 @@
 #include "nsPluginHost.h"
 #include "nsPluginSafety.h"
 #include "nsPluginLogging.h"
-#include "nsIPrivateBrowsingService.h"
 #include "nsContentUtils.h"
 
 #include "nsIDocument.h"
@@ -152,7 +151,7 @@ nsresult nsNPAPIPluginInstance::Initialize(nsNPAPIPlugin *aPlugin, nsIPluginInst
       PL_strcpy(mMIMEType, aMIMEType);
     }
   }
-
+  
   return Start();
 }
 
@@ -1143,7 +1142,7 @@ nsNPAPIPluginInstance::GetPluginAPIVersion(PRUint16* version)
 }
 
 nsresult
-nsNPAPIPluginInstance::PrivateModeStateChanged()
+nsNPAPIPluginInstance::PrivateModeStateChanged(bool enabled)
 {
   if (RUNNING != mRunning)
     return NS_OK;
@@ -1155,23 +1154,15 @@ nsNPAPIPluginInstance::PrivateModeStateChanged()
 
   NPPluginFuncs* pluginFunctions = mPlugin->PluginFuncs();
 
-  if (pluginFunctions->setvalue) {
-    PluginDestructionGuard guard(this);
-    
-    nsCOMPtr<nsIPrivateBrowsingService> pbs = do_GetService(NS_PRIVATE_BROWSING_SERVICE_CONTRACTID);
-    if (pbs) {
-      bool pme = false;
-      nsresult rv = pbs->GetPrivateBrowsingEnabled(&pme);
-      if (NS_FAILED(rv))
-        return rv;
+  if (!pluginFunctions->setvalue)
+    return NS_ERROR_FAILURE;
 
-      NPError error;
-      NPBool value = static_cast<NPBool>(pme);
-      NS_TRY_SAFE_CALL_RETURN(error, (*pluginFunctions->setvalue)(&mNPP, NPNVprivateModeBool, &value), this);
-      return (error == NPERR_NO_ERROR) ? NS_OK : NS_ERROR_FAILURE;
-    }
-  }
-  return NS_ERROR_FAILURE;
+  PluginDestructionGuard guard(this);
+    
+  NPError error;
+  NPBool value = static_cast<NPBool>(enabled);
+  NS_TRY_SAFE_CALL_RETURN(error, (*pluginFunctions->setvalue)(&mNPP, NPNVprivateModeBool, &value), this);
+  return (error == NPERR_NO_ERROR) ? NS_OK : NS_ERROR_FAILURE;
 }
 
 class DelayUnscheduleEvent : public nsRunnable {
diff --git a/dom/plugins/base/nsNPAPIPluginInstance.h b/dom/plugins/base/nsNPAPIPluginInstance.h
index d8b4a87e342..1bf381b0808 100644
--- a/dom/plugins/base/nsNPAPIPluginInstance.h
+++ b/dom/plugins/base/nsNPAPIPluginInstance.h
@@ -204,7 +204,7 @@ public:
 
   already_AddRefed<nsPIDOMWindow> GetDOMWindow();
 
-  nsresult PrivateModeStateChanged();
+  nsresult PrivateModeStateChanged(bool aEnabled);
 
   nsresult GetDOMElement(nsIDOMElement* *result);
 
diff --git a/dom/plugins/base/nsPluginHost.cpp b/dom/plugins/base/nsPluginHost.cpp
index 560e2192e33..8f74705b95c 100644
--- a/dom/plugins/base/nsPluginHost.cpp
+++ b/dom/plugins/base/nsPluginHost.cpp
@@ -86,7 +86,6 @@
 #include "nsIScriptChannel.h"
 #include "nsIBlocklistService.h"
 #include "nsVersionComparator.h"
-#include "nsIPrivateBrowsingService.h"
 #include "nsIObjectLoadingContent.h"
 #include "nsIWritablePropertyBag2.h"
 #include "nsPluginStreamListenerPeer.h"
@@ -357,7 +356,6 @@ nsPluginHost::nsPluginHost()
     mozilla::services::GetObserverService();
   if (obsService) {
     obsService->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
-    obsService->AddObserver(this, NS_PRIVATE_BROWSING_SWITCH_TOPIC, false);
 #ifdef MOZ_WIDGET_ANDROID
     obsService->AddObserver(this, "application-foreground", false);
     obsService->AddObserver(this, "application-background", false);
@@ -3330,12 +3328,6 @@ NS_IMETHODIMP nsPluginHost::Observe(nsISupports *aSubject,
     Destroy();
     sInst->Release();
   }
-  if (!nsCRT::strcmp(NS_PRIVATE_BROWSING_SWITCH_TOPIC, aTopic)) {
-    // inform all active plugins of changed private mode state
-    for (PRUint32 i = 0; i < mInstances.Length(); i++) {
-      mInstances[i]->PrivateModeStateChanged();
-    }
-  }
 #ifdef MOZ_WIDGET_ANDROID
   if (!nsCRT::strcmp("application-background", aTopic)) {
     for(PRUint32 i = 0; i < mInstances.Length(); i++) {
diff --git a/dom/plugins/base/nsPluginInstanceOwner.cpp b/dom/plugins/base/nsPluginInstanceOwner.cpp
index bdf34a35cb3..b37e6af80d0 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.cpp
+++ b/dom/plugins/base/nsPluginInstanceOwner.cpp
@@ -100,6 +100,7 @@ using mozilla::DefaultXDisplay;
 #include "nsIScrollableFrame.h"
 #include "nsIImageLoadingContent.h"
 #include "nsIObjectLoadingContent.h"
+#include "nsIDocShell.h"
 
 #include "nsContentCID.h"
 #include "nsWidgetsCID.h"
@@ -404,10 +405,12 @@ nsPluginInstanceOwner::~nsPluginInstanceOwner()
   }
 }
 
-NS_IMPL_ISUPPORTS3(nsPluginInstanceOwner,
+NS_IMPL_ISUPPORTS5(nsPluginInstanceOwner,
                    nsIPluginInstanceOwner,
                    nsIPluginTagInfo,
-                   nsIDOMEventListener)
+                   nsIDOMEventListener,
+                   nsIPrivacyTransitionObserver,
+                   nsISupportsWeakReference)
 
 nsresult
 nsPluginInstanceOwner::SetInstance(nsNPAPIPluginInstance *aInstance)
@@ -427,6 +430,17 @@ nsPluginInstanceOwner::SetInstance(nsNPAPIPluginInstance *aInstance)
 
   mInstance = aInstance;
 
+  nsCOMPtr<nsIDocument> doc;
+  GetDocument(getter_AddRefs(doc));
+  if (doc) {
+    nsCOMPtr<nsPIDOMWindow> domWindow = doc->GetWindow();
+    if (domWindow) {
+      nsCOMPtr<nsIDocShell> docShell = domWindow->GetDocShell();
+      if (docShell)
+        docShell->AddWeakPrivacyTransitionObserver(this);
+    }
+  }
+
   return NS_OK;
 }
 
@@ -3798,6 +3812,11 @@ void nsPluginInstanceOwner::FixUpURLS(const nsString &name, nsAString &value)
   }
 }
 
+NS_IMETHODIMP nsPluginInstanceOwner::PrivateModeChanged(bool aEnabled)
+{
+  return mInstance ? mInstance->PrivateModeStateChanged(aEnabled) : NS_OK;
+}
+
 // nsPluginDOMContextMenuListener class implementation
 
 nsPluginDOMContextMenuListener::nsPluginDOMContextMenuListener()
diff --git a/dom/plugins/base/nsPluginInstanceOwner.h b/dom/plugins/base/nsPluginInstanceOwner.h
index d2c77986158..f6c764c2366 100644
--- a/dom/plugins/base/nsPluginInstanceOwner.h
+++ b/dom/plugins/base/nsPluginInstanceOwner.h
@@ -52,10 +52,12 @@
 #include "nsCOMPtr.h"
 #include "nsIPluginInstanceOwner.h"
 #include "nsIPluginTagInfo.h"
+#include "nsIPrivacyTransitionObserver.h"
 #include "nsIDOMEventListener.h"
 #include "nsIScrollPositionListener.h"
 #include "nsPluginHost.h"
 #include "nsPluginNativeWindow.h"
+#include "nsWeakReference.h"
 #include "gfxRect.h"
 
 // X.h defines KeyPress
@@ -103,7 +105,9 @@ namespace mozilla {
 class nsPluginInstanceOwner : public nsIPluginInstanceOwner,
                               public nsIPluginTagInfo,
                               public nsIDOMEventListener,
-                              public nsIScrollPositionListener
+                              public nsIScrollPositionListener,
+                              public nsIPrivacyTransitionObserver,
+                              public nsSupportsWeakReference
 {
 public:
   nsPluginInstanceOwner();
@@ -111,6 +115,7 @@ public:
   
   NS_DECL_ISUPPORTS
   NS_DECL_NSIPLUGININSTANCEOWNER
+  NS_DECL_NSIPRIVACYTRANSITIONOBSERVER
   
   NS_IMETHOD GetURL(const char *aURL, const char *aTarget,
                     nsIInputStream *aPostStream,