gclient: Map origin/foo to refs/remotes/origin/foo

Bug: 1200657
Change-Id: Ib719b984a71cd944bbccf3ec7065aaa17f60e638
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2838026Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

gclient_scm.py

@@ -488,6 +488,8 @@ class GitWrapper(SCMWrapper):
       # If a dependency is not pinned, track the default remote branch.
       revision = scm.GIT.GetRemoteHeadRef(self.checkout_path, self.url,
                                           self.remote)
+    if revision.startswith('origin/'):
+      revision = 'refs/remotes/' + revision
 
     if managed:
       self._DisableHooks()