Grant Files.app access for mount points added after its launch.

Previous implementation of GrantFullAccessToExtension() granted permissions
only for paths that are mounted at that moment, and required hack for
one dynamically mounted path, namely, Google Drive directory.

It's not what is meant for GrantFullAccessToExtension(). Rather, it
should just simply allow access for the extension any time.
In multi-profile settings, more directories, i.e., Downloads/Drive
directories from other profiles are going to be dynamically added.

BUG=337705

Review URL: https://codereview.chromium.org/148233008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247852 0039d316-1c4b-4281-b951-d872f2087c98
Add accelerator table entries for VKEY_BROWSER_(BACK|FORWARD) on linux

This registers accelerator table entries for VKEY_BROWSER_(BACK|FORWARD)
to IDC_(BACK|FORWARD) for linux platforms (linux desktop and ChromeOS) so
that hardward back/forward keys navigate the browser.

BUG=338945

Review URL: https://codereview.chromium.org/149273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247853 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247853