Adding histograms for server requests. Also, some preparations for supposed future sending of diagnostic JS stacks.
BUG=164227
TEST=After starting the extension, open chrome://histograms and make sure you see GoogleNow.Event histogram. Check for both component and non-component extensions. Wait for several days and check that the data appears in the dashboard.
Review URL: https://chromiumcodereview.appspot.com/
13356002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@193971 0039d316-1c4b-4281-b951-d872f2087c98