GitLab

Create an ExtensionErrorController to be in charge of ExtensionErrorUI so that
ExtensionService doens't have to know as much about it.
And, of course, add a few tests for otherwise untested behavior.

BUG=351891

Review URL: https://codereview.chromium.org/227373007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262893 0039d316-1c4b-4281-b951-d872f2087c98