Bug 1065880 - Measure e10s usage through telemetry. r=bsmedberg,mconley

browser/base/content/browser.js

@@ -1097,6 +1097,8 @@ var gBrowserInit = {
       TabCrashReporter.init();
 #endif
 
+    Services.telemetry.getHistogramById("E10S_WINDOW").add(gMultiProcessBrowser);
+
     if (mustLoadSidebar) {
       let sidebar = document.getElementById("sidebar");
       let sidebarBox = document.getElementById("sidebar-box");

toolkit/components/telemetry/Histograms.json

@@ -6594,5 +6594,25 @@
     "kind": "enumerated",
     "n_values": 3,
     "description": "Doorhanger shown = 0, Disable = 1, Enable = 2"
+  },
+  "E10S_AUTOSTART": {
+    "expires_in_version": "never",
+    "kind": "boolean",
+    "description": "Whether a session is set to autostart e10s windows"
+  },
+  "E10S_WINDOW": {
+    "expires_in_version": "never",
+    "kind": "boolean",
+    "description": "Whether a browser window is set as an e10s window"
+  },
+  "E10S_STILL_ACCEPTED_FROM_PROMPT": {
+    "expires_in_version": "40",
+    "kind": "boolean",
+    "description": "Whether a user who accepted e10s from the prompt is still using e10s"
+  },
+  "E10S_BLOCKED_FROM_RUNNING": {
+    "expires_in_version": "40",
+    "kind": "boolean",
+    "description": "Whether the e10s pref was set but it was blocked from running due to blacklisted conditions"
   }
 }

toolkit/xre/nsAppRunner.cpp

@@ -4524,9 +4524,19 @@ bool
 mozilla::BrowserTabsRemoteAutostart()
 {
   if (!gBrowserTabsRemoteAutostartInitialized) {
-    gBrowserTabsRemoteAutostart = !gSafeMode &&
-                                  Preferences::GetBool("browser.tabs.remote.autostart", false);
+    bool prefEnabled = Preferences::GetBool("browser.tabs.remote.autostart", false);
+    gBrowserTabsRemoteAutostart = !gSafeMode && prefEnabled;
     gBrowserTabsRemoteAutostartInitialized = true;
+
+    mozilla::Telemetry::Accumulate(mozilla::Telemetry::E10S_AUTOSTART, gBrowserTabsRemoteAutostart);
+    if (Preferences::GetBool("browser.enabledE10SFromPrompt", false)) {
+      mozilla::Telemetry::Accumulate(mozilla::Telemetry:E10S_STILL_ACCEPTED_FROM_PROMPT,
+                                     gBrowserTabsRemoteAutostart);
+    }
+    if (prefEnabled) {
+      mozilla::Telemetry::Accumulate(mozilla::Telemetry::E10S_BLOCKED_FROM_RUNNING,
+                                     !gBrowserTabsRemoteAutostart);
+    }
   }
 
   return gBrowserTabsRemoteAutostart;