Change chromium fetch spec to use master as the git-svn ref.

R=vadimsh@chromium.org
BUG=366924

Review URL: https://codereview.chromium.org/450863002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@288205 0039d316-1c4b-4281-b951-d872f2087c98

recipes/chromium.py

@@ -28,7 +28,7 @@ class Chromium(recipe_util.Recipe):
       'solutions': [solution],
       'svn_url': 'svn://svn.chromium.org/chrome',
       'svn_branch': 'trunk/src',
-      'svn_ref': 'git-svn',
+      'svn_ref': 'master',
     }
     if props.get('submodule_git_svn_spec'):
       spec['submodule_git_svn_spec'] = props['submodule_git_svn_spec']