Fix bug causing tab favicon media indicator to not turn off.
Root cause: MediaStreamCaptureIndicator::CaptureDevicesClosed() is being called with the original render_process_id/render_view_id, rather than the current ones associated with a WebContents instance. This is because media capture was launched by an extension, and MediaStreamManager only knows what the ID pair was at the time the media capture was started.
Changes include:
1. Tore-out the existing "find a tab" code.
2. Added an alias mapping with a LookUp function that finds a WebContents instance by current or any previously-known ID pair.
3. Fixed possible de-refs of WebContents pointers after the instance is destroyed.
4. Clean-ups of comments/naming, and minor code reorganization.
BUG=171077
TEST=Confirmed, by manually running a debug-build browser (on Win7 and Linux), that existing functionality is not broken and that the bug is fixed.
TBR=ben
Review URL: https://chromiumcodereview.appspot.com/
12035046
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@179490 0039d316-1c4b-4281-b951-d872f2087c98