Bug 1366808: Add telemetry probe for about:restartrequired page. r=jimm

browser/modules/ContentCrashHandlers.jsm

@@ -329,6 +329,12 @@ var TabCrashHandler = {
 
     browser.docShell.displayLoadError(Cr.NS_ERROR_BUILDID_MISMATCH, uri, null);
     tab.setAttribute("crashed", true);
+
+    // Make sure to only count once even if there are multiple windows
+    // that will all show about:restartrequired.
+    if (this._crashedTabCount == 1) {
+      Services.telemetry.getHistogramById("FX_CONTENT_BUILDID_MISMATCH").add(1);
+    }
   },
 
   /**

toolkit/components/telemetry/Histograms.json

@@ -12563,6 +12563,15 @@
     "kind": "count",
     "releaseChannelCollection": "opt-out",
     "description": "Counts the number of times that about:tabcrashed was unloaded without submitting."
+  },
+  "FX_CONTENT_BUILDID_MISMATCH": {
+    "record_in_processes": ["main"],
+    "alert_emails": ["spohl@mozilla.com"],
+    "bug_numbers": [1366808],
+    "expires_in_version": "never",
+    "kind": "count",
+    "releaseChannelCollection": "opt-out",
+    "description": "Counts the number of times that about:restartrequired appeared."
   },
    "D3D9_COMPOSITING_FAILURE_ID": {
     "record_in_processes": ["main", "content"],

toolkit/components/telemetry/histogram-whitelists.json

@@ -1636,6 +1636,7 @@
     "FX_CONTENT_CRASH_DUMP_UNAVAILABLE",
     "FX_CONTENT_CRASH_NOT_SUBMITTED",
     "FX_CONTENT_CRASH_PRESENTED",
+    "FX_CONTENT_BUILDID_MISMATCH",
     "FX_SESSION_RESTORE_SEND_UPDATE_CAUSED_OOM",
     "FX_TOUCH_USED",
     "GEOLOCATION_ERROR",