Bug 971171 - Measure with telemetry how many times people see about:newtab. r=ttaubert,bsmedberg

browser/base/content/browser.js

@@ -1005,8 +1005,13 @@ var gBrowserInit = {
       }
       // Note: loadOneOrMoreURIs *must not* be called if window.arguments.length >= 3.
       // Such callers expect that window.arguments[0] is handled as a single URI.
-      else
+      else {
+        if (uriToLoad == "about:newtab" &&
+            Services.prefs.getBoolPref("browser.newtabpage.enabled")) {
+          Services.telemetry.getHistogramById("NEWTAB_PAGE_SHOWN").add(true);
+        }
         loadOneOrMoreURIs(uriToLoad);
+      }
     }
 
 #ifdef MOZ_SAFE_BROWSING