Extension Storage API: expose storage quota information to extensions, via:

chrome/browser/extensions/settings/testing_settings_storage.cc

Index: chrome/browser/extensions/settings/testing_settings_storage.cc
diff --git a/chrome/browser/extensions/settings/testing_settings_storage.cc b/chrome/browser/extensions/settings/testing_settings_storage.cc
index fc78991f881c5f6ebbacc3f65bd6638fb4fe5c17..897a86a91c70624ce2b6b08a10df47c97185b059 100644
--- a/chrome/browser/extensions/settings/testing_settings_storage.cc
+++ b/chrome/browser/extensions/settings/testing_settings_storage.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -37,6 +37,12 @@ void TestingSettingsStorage::SetFailAllRequests(bool fail_all_requests) {
   fail_all_requests_ = fail_all_requests;
 }
 
+size_t TestingSettingsStorage::GetBytesInUse() {
+  // Let SettingsStorageQuotaEnforcer implement this.
+  NOTREACHED() << "Not implemented";
+  return 0;
+}
+
 SettingsStorage::ReadResult TestingSettingsStorage::Get(
     const std::string& key) {
   return Get(CreateVector(key));