[Telemetry] Fix flaky BoundingBoxNotFoundExceptions when measuring Speed Index.

There's no reason we have to restrict our initial flash search to the first
frame. Instead, just search every frame until we find it.

BUG=
TBR=slamm@chromium.org

Review URL: https://codereview.chromium.org/143663006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250519 0039d316-1c4b-4281-b951-d872f2087c98
Add additional way to start Activities for PendingIntents

Sometimes we need to start Activities using a PendingIntent
and its IntentSender.  Add a pathway for doing so.

BUG=341556

Review URL: https://codereview.chromium.org/146623008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250520 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250519
SVN changes up to revision 250520