Random clean up on Drive related code.

BUG=none

Review URL: https://codereview.chromium.org/28023002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229638 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229638
Support hidpi avatar icons in avatar menus and buttons

Derive from CanvasImageSource to draw avatar icons for title menu and buttons. Also make the title menu "etching" less ugly, especially in fullscreen.

BUG=306252

Review URL: https://codereview.chromium.org/27746002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229639 0039d316-1c4b-4281-b951-d872f2087c98
Break the dependency BackTexture had on the entire Decoder.

BUG=

Review URL: https://codereview.chromium.org/27762003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229640 0039d316-1c4b-4281-b951-d872f2087c98
Add comment describing a fix made to mesa.
The fix is in: https://codereview.chromium.org/27740005

BUG=308715

Review URL: https://codereview.chromium.org/27764003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229641 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229640
SVN changes up to revision 229641