Bug 1011136 - Add a histogram for plugin startup duration. r=bsmedberg

dom/plugins/base/nsPluginHost.cpp

@@ -719,10 +719,10 @@ void nsPluginHost::OnPluginInstanceDestroyed(nsPluginTag* aPluginTag)
   // Another reason not to unload immediately is that loading is expensive,
   // and it is better to leave popular plugins loaded.
   //
-  // Our default behavior is to try to unload a plugin three minutes after
-  // its last instance is destroyed. This seems like a reasonable compromise
-  // that allows us to reclaim memory while allowing short state retention
-  // and avoid perf hits for loading popular plugins.
+  // Our default behavior is to try to unload a plugin after a pref-controlled
+  // delay once its last instance is destroyed. This seems like a reasonable
+  // compromise that allows us to reclaim memory while allowing short state
+  // retention and avoid perf hits for loading popular plugins.
   if (!hasInstance) {
     if (UnloadPluginsASAP()) {
       aPluginTag->TryUnloadPlugin(false);

dom/plugins/ipc/PluginProcessParent.cpp

@@ -11,6 +11,7 @@
 
 #include "mozilla/ipc/BrowserProcessSubThread.h"
 #include "mozilla/plugins/PluginMessageUtils.h"
+#include "mozilla/Telemetry.h"
 
 using std::vector;
 using std::string;
@@ -75,6 +76,7 @@ PluginProcessParent::Launch(int32_t timeoutMs)
 
     vector<string> args;
     args.push_back(MungePluginDsoPath(mPluginFilePath));
+    Telemetry::AutoTimer<Telemetry::PLUGIN_STARTUP_MS> timer;
     return SyncLaunch(args, timeoutMs, selectedArchitecture);
 }
 

toolkit/components/telemetry/Histograms.json

@@ -2328,6 +2328,14 @@
     "n_buckets": 20,
     "description": "Time spent loading plugin DLL and obtaining metadata (ms)"
   },
+  "PLUGIN_STARTUP_MS": {
+    "expires_in_version": "never",
+    "kind": "exponential",
+    "high": "5000",
+    "n_buckets": 20,
+    "extended_statistics_ok": true,
+    "description": "Time spent starting up plugins (ms)"
+  },
   "PLUGIN_SHUTDOWN_MS": {
     "expires_in_version": "never",
     "kind": "exponential",