Have ExtensionService notify ThemeService directly for themes

This is a retry of r169875, hopefully with fewer regressions.

This time, I simply notify the theme service (instantiating it
if necessary) when a theme extension is installed.

This should avoid the theme regression since that path is not
taken on browser startup.

BUG=161203
[email protected]

Review URL: https://codereview.chromium.org/11411330

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@170880 0039d316-1c4b-4281-b951-d872f2087c98
5 files changed