Ensure that extensions are not loaded when reporting timeout.

In order to ensure investigation of the issue when extensions are not
yet loaded after 5 minutes (timeouted), double-check pending list.
For the case if there are policy configured extensions that are
installed, but not loaded, new metrics will be reported:
Extensions.ForceInstalledTimedOutAndNotInstalledCount

BUG=787970
TEST=Unit tests updated

Change-Id: I2ade477fe96e9b32546c4ce819c4316ff31b17bd
Reviewed-on: https://chromium-review.googlesource.com/1135246
Commit-Queue: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575583}
3 files changed