Retry npm calls since they seem a bit unreliable.

utils.py

 #!/usr/bin/python
 # Copyright 2014 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.
 
 """Utilities for all our deps-management stuff."""
 
 import hashlib
 import os
 import shutil
 import sys
 import subprocess
 import tarfile
+import time
 import zipfile
 
 
+def RunSubprocessWithRetry(cmd):
+  """Invokes the subprocess and backs off exponentially on fail."""
+  for i in range(5):
+    try:
+      subprocess.check_call(cmd)
+      return
+    except subprocess.CalledProcessError as exception:
+      backoff = pow(2, i)
+      print 'Got %s, retrying in %d seconds...' % (exception, backoff)
+      time.sleep(backoff)
+  
+  print 'Giving up.'
+  raise exception
+
+
 def DownloadFilesFromGoogleStorage(path):
   print 'Downloading files in %s...' % path
 
   extension = 'bat' if 'win32' in sys.platform else 'py'
   cmd = ['download_from_google_storage.%s' % extension,
          '--bucket=chromium-webrtc-resources',
          '--auto_platform',
          '--recursive',
          '--directory', path]
   subprocess.check_call(cmd)
@@ skipping 49 matching lines @@
 
 def GetPlatform():
   if sys.platform.startswith('win'):
     return 'win'
   if sys.platform.startswith('linux'):
     return 'linux'
   if sys.platform.startswith('darwin'):
     return 'mac'
   raise Exception("Can't run on platform %s." % sys.platform)