Media Galleries API: Fix MediaGalleriesPreferences finders race.

Unfortunately, MediaGalleriesPreferences now relies on two async finders during initialization, and currently has a race, where the finders don't return their devices until sometimes unspecified later. This adds an EnsureInitialized mechanic similar to StorageMonitor to solve that. Kind of ugly.

BUG=151701,295880

Review URL: https://codereview.chromium.org/24269007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226127 0039d316-1c4b-4281-b951-d872f2087c98
Move Wallet error codes from notification text to tooltip.

R=estade@chromium.org
BUG=262230
TEST=wallet errors show only in tooltips

Review URL: https://codereview.chromium.org/25148002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226128 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226128