Allow overlapping sync and async startup requests
On Android we can get a second request to start the browser while
the an asynchronous request is in progress. Since the second
request may be synchronous, we may have switch to completing
initialization synchronously. This patch handles this by tracking
which initialization tasks have been run, and running the remaining
initialization tasks.
BUG=260574
Review URL: https://chromiumcodereview.appspot.com/
22691002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@219795 0039d316-1c4b-4281-b951-d872f2087c98