app_shell: Convert ExtensionsWebContentsObserver to BrowserContext from Profile

And make it use ExtensionRegistry in one more place. It's used by ExtensionHost
and this is a small step toward eliminating chrome dependencies.

BUG=309909
TEST=browser_tests

Review URL: https://codereview.chromium.org/134393003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244418 0039d316-1c4b-4281-b951-d872f2087c98
Clean-up: Remove the very last few uses of base::Time from src/media/

This (finally) completes the effort to remove all uses of base::Time as a clock for tracking time passage in the media component.  For more info, please see src/media/PRESUBMIT.py.

Review URL: https://codereview.chromium.org/134603005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244419 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244419