tools/android/loading Loading trace database improvements

tools/android/loading/loading_trace_database.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.
 
 """Represents a database of on-disk traces."""
 
 import json
 from google_storage_util import ReadFromGoogleStorage
 
 
 class LoadingTraceDatabase(object):
   def __init__(self, traces_dict):
     """traces_dict is a dictionary mapping filenames of traces to metadata
        about those traces."""
     self._traces_dict = traces_dict
 
-  def AddTrace(self, filename, trace_dict):
-    """Adds a mapping from |filename| to |trace_dict| into the database."""
-    assert filename not in self._traces_dict
+  def SetTrace(self, filename, trace_dict):
+    """Sets a mapping from |filename| to |trace_dict| into the database.
+    If there is an existing mapping for filename, it is replaced.
+    """
     self._traces_dict[filename] = trace_dict
 
   def GetTraceFilesForURL(self, url):
     """Given a URL, returns the set of filenames of traces that were generated
        for this URL."""
     trace_files = [f for f in self._traces_dict.keys()
         if self._traces_dict[f]["url"] == url]
     return trace_files
 
   def ToJsonDict(self):
@@ skipping 16 matching lines @@
     """Returns an instance from a json file saved by ToJsonFile()."""
     with open(json_path) as input_file:
       return cls.FromJsonDict(json.load(input_file))
 
   @classmethod
   def FromJsonFileInGoogleStorage(cls, json_google_storage_path):
     """Returns an instance from a json file in Google Storage whose contents
        were generated by ToJsonFile()."""
     json_string = ReadFromGoogleStorage(json_google_storage_path)
     return cls.FromJsonDict(json.loads(json_string))