browser-extension: fall back to static info when resolveRev fails
Created by: chrismwendt
ensureRevisionsAreCloned
can fail when the current repository is private and the configured Sourcegraph URL is Sourcegraph.com (we block requests that could leak private info).
When the call fails for that reason, this change falls back to the FileInfo
obtained directly from the page.
I also removed a redundant copy of this function.
Related: https://github.com/sourcegraph/sourcegraph/issues/852 (this PR doesn't resolve that issue)
This PR does not need to update the CHANGELOG because