If a preferences file references a theme which is from an old version, or whose images have failed to process correctly, drop back to the default theme.
If a preferences file references a theme which is from an old version, or whose images have failed to process correctly, drop back to the default theme.

BUG= http://crbug.com/20263
TEST= Use a preferences file from an older version of Chrome that has a theme installed, and open Chrome.  Observe that Chrome opens using the default theme.

Review URL: http://codereview.chromium.org/175013

git-svn-id: http://src.chromium.org/svn/trunk/src@24830 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 60dbf7ec10148a5b354203d6c722f8f436f6e32d
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser