Convert ebuild to pull chrome sources from git.

Re-landing this:

https://chromium-review.googlesource.com/212790

It should work now, after this change to gclient:

https://codereview.chromium.org/490233003

... and after rolling that change into the manifest:

https://chromium-review.googlesource.com/#/c/213524/
https://chrome-internal-review.googlesource.com/#/c/173395/

BUG=chromium:376027
TEST=scripts/cros_mark_chrome_as_stable_unittest.py

Change-Id: I20c2a6d3a221fae0a3849628b688cded996834b4
Reviewed-on: https://chromium-review.googlesource.com/213460
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: Stefan Zager <szager@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index 3ab8d75..5237255 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -52,9 +52,9 @@
 from chromite.lib import cleanup
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
-from chromite.lib import gclient
 from chromite.lib import gerrit
 from chromite.lib import git
+from chromite.lib import gob_util
 from chromite.lib import osutils
 from chromite.lib import patch as cros_patch
 from chromite.lib import parallel
@@ -917,9 +917,8 @@
   if options.chrome_rev:
     chrome_rev = options.chrome_rev
   if chrome_rev == constants.CHROME_REV_TOT:
-    # Build the TOT Chrome revision.
-    svn_url = gclient.GetBaseURLs()[0]
-    options.chrome_version = gclient.GetTipOfTrunkSvnRevision(svn_url)
+    options.chrome_version = gob_util.GetTipOfTrunkRevision(
+        constants.CHROMIUM_GOB_URL)
     options.chrome_rev = constants.CHROME_REV_SPEC
 
   # If it's likely we'll need to build Chrome, fetch the source.
@@ -1241,7 +1240,7 @@
                           action='callback', dest='chrome_version',
                           callback=_CheckChromeVersionOption,
                           help=('Used with SPEC logic to force a particular '
-                                'SVN revision of chrome rather than the '
+                                'git revision of chrome rather than the '
                                 'latest.'))
   group.add_remote_option('--clobber', action='store_true', dest='clobber',
                           default=False,