sandwich: Implements filter-cache sub-command.

tools/android/loading/chrome_cache.py

Index: tools/android/loading/chrome_cache.py
diff --git a/tools/android/loading/chrome_cache.py b/tools/android/loading/chrome_cache.py
index d6d65a265690fdc4a2fa9fea4a3238a4dd7511e6..40d15bb7dd07f78aa4bdb5f556e26e7b16c039e5 100644
--- a/tools/android/loading/chrome_cache.py
+++ b/tools/android/loading/chrome_cache.py
@@ -8,6 +8,7 @@
 from datetime import datetime
 import json
 import os
+import shutil
 import subprocess
 import sys
 import tempfile
@@ -278,6 +279,32 @@ class CacheBackend(object):
     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.')