ensure_goma for goma canary

scripts/slave/recipe_modules/goma/api.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from recipe_engine import recipe_api
 
 class GomaApi(recipe_api.RecipeApi):
   """GomaApi contains helper functions for using goma."""
 
   def update_goma_canary(self):
     """Returns a step for updating goma canary."""
+    # deprecated? switch to use ensure_goma with canary=True.
     # for git checkout, should use @refs/heads/master to use head.
     head = 'refs/heads/master'
     # TODO(phajdan.jr): Remove path['build'] usage, http://crbug.com/437264 .
     self.m.gclient('update goma canary',
                    ['sync', '--verbose', '--force',
                     '--revision', 'build/goma@%s' % head],
                    cwd=self.m.path['build'])
 
-  def ensure_goma(self, goma_dir):
+  def ensure_goma(self, goma_dir, canary=False):
     # TODO(iannucci): switch to CIPD (https://goto.google.com/toxxq).
+    args=[
+        '--target-dir', goma_dir,
+        '--download-from-google-storage-path',
+        self.m.depot_tools.download_from_google_storage_path
+    ]
+    if canary:
+      args += ['--canary']
     self.m.python(
       name='ensure_goma',
       script=self.resource('ensure_goma.py'),
-      args=[
-        '--target-dir', goma_dir,
-        '--download-from-google-storage-path',
-        self.m.depot_tools.download_from_google_storage_path
-      ],
+      args=args,
       infra_step=True)