Properly report blacklisted extension errors (currently, blacklisted extensions don't send an install error notification, so the loading bubble persists forever).
Properly report blacklisted extension errors (currently, blacklisted extensions don't send an install error notification, so the loading bubble persists forever).

BUG=none
TEST=install a blacklisted extension

Review URL: http://codereview.chromium.org/418031

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@32702 0039d316-1c4b-4281-b951-d872f2087c98

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