tools/android/loading Loading trace database improvements

tools/android/loading/cloud/backend/google_storage_accessor.py

 # Copyright 2016 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 gcloud import storage
+import gcloud.exceptions
+import gcloud.storage
 
 
 class GoogleStorageAccessor(object):
   """Utility class providing helpers for Google Cloud Storage.
   """
   def __init__(self, credentials, project_name, bucket_name):
     """project_name is the name of the Google Cloud project.
     bucket_name is the name of the bucket that is used for Cloud Storage calls.
     """
     self._credentials = credentials
     self._project_name = project_name
     self._bucket_name = bucket_name
 
   def _GetStorageClient(self):
     """Returns the storage client associated with the project"""
-    return storage.Client(project = self._project_name,
-                          credentials = self._credentials)
+    return gcloud.storage.Client(project = self._project_name,
+                                 credentials = self._credentials)
 
   def _GetStorageBucket(self, storage_client):
     return storage_client.get_bucket(self._bucket_name)
 
+  def DownloadAsString(self, remote_filename):
+    """Returns the content of a remote file as a string, or None if the file
+    does not exist.
+    """
+    client = self._GetStorageClient()
+    bucket = self._GetStorageBucket(client)
+    blob = bucket.get_blob(remote_filename)
+    if not blob:
+      return None
+    try:
+      return blob.download_as_string()
+    except gcloud.exceptions.NotFound:
+      return None
+
   def UploadFile(self, filename_src, filename_dest):
     """Uploads a file to Google Cloud Storage
 
     Args:
       filename_src: name of the local file
       filename_dest: name of the file in Google Cloud Storage
 
     Returns:
       The URL of the file in Google Cloud Storage.
     """
@@ skipping 13 matching lines @@
 
     Returns:
       The URL of the file in Google Cloud Storage.
     """
     client = self._GetStorageClient()
     bucket = self._GetStorageBucket(client)
     blob = bucket.blob(filename_dest)
     blob.upload_from_string(data_string)
     return blob.public_url