GitLab

* Base name duplication is handled and should be tested in ResourceMetadata.
* OpenFile's behavior can be tested in OpenFileOperation.

Along the way did some clean up.

BUG=none

Review URL: https://chromiumcodereview.appspot.com/23606018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221659 0039d316-1c4b-4281-b951-d872f2087c98