sandwich: Implements filter-cache sub-command.

tools/android/loading/chrome_cache.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.
 
 """Takes care of manipulating the chrome's HTTP cache.
 """
 
 from datetime import datetime
 import json
 import os
+import shutil
 import subprocess
 import sys
 import tempfile
 import zipfile
 
 _SRC_DIR = os.path.abspath(os.path.join(
     os.path.dirname(__file__), '..', '..', '..'))
 
 sys.path.append(os.path.join(_SRC_DIR, 'build', 'android'))
 from pylib import constants
@@ skipping 250 matching lines @@
         self._cache_directory_path,
         self._cache_backend_type,
         operation]
     editor_tool_cmd.extend(args)
     process = subprocess.Popen(editor_tool_cmd, stdout=subprocess.PIPE)
     stdout_data, _ = process.communicate()
     assert process.returncode == 0
     return stdout_data
 
 
+def ApplyUrlWhitelistToCacheArchive(cache_archive_path,
+                                    whitelisted_urls,
+                                    output_cache_archive_path):
+  """Generate a new cache archive containing only whitelisted urls.
+
+  Args:
+    cache_archive_path: Path of the cache archive to apply the white listing.
+    whitelisted_urls: Set of url to keep in cache.
+    output_cache_archive_path: Destination path of cache archive containing only
+      white-listed urls.
+  """
+  cache_temp_directory = tempfile.mkdtemp(suffix='.cache')
+  try:
+    UnzipDirectoryContent(cache_archive_path, cache_temp_directory)
+    backend = CacheBackend(cache_temp_directory, 'simple')
+    cached_urls = backend.ListKeys()
+    for cached_url in cached_urls:
+      if cached_url not in whitelisted_urls:
+        backend.DeleteKey(cached_url)
+    for cached_url in backend.ListKeys():
+      assert cached_url in whitelisted_urls
+    ZipDirectoryContent(cache_temp_directory, output_cache_archive_path)
+  finally:
+    shutil.rmtree(cache_temp_directory)
+
+
 if __name__ == '__main__':
   import argparse
   parser = argparse.ArgumentParser(description='Tests cache back-end.')
   parser.add_argument('cache_path', type=str)
   parser.add_argument('backend_type', type=str, choices=BACKEND_TYPES)
   command_line_args = parser.parse_args()
 
   cache_backend = CacheBackend(
       cache_directory_path=command_line_args.cache_path,
       cache_backend_type=command_line_args.backend_type)
   keys = cache_backend.ListKeys()
   print '{}\'s HTTP response header:'.format(keys[0])
   print cache_backend.GetStreamForKey(keys[0], 0)
   cache_backend.DeleteKey(keys[1])
   assert keys[1] not in cache_backend.ListKeys()