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

chrome/browser/extensions/settings/failing_settings_storage.cc

-// 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.
 
 #include "chrome/browser/extensions/settings/failing_settings_storage.h"
 
+#include "base/logging.h"
+
 namespace extensions {
 
 namespace {
 
 const char* kGenericErrorMessage = "Failed to initialize settings";
 
 SettingsStorage::ReadResult ReadResultError() {
   return SettingsStorage::ReadResult(kGenericErrorMessage);
 }
 
 SettingsStorage::WriteResult WriteResultError() {
   return SettingsStorage::WriteResult(kGenericErrorMessage);
 }
 
 }  // namespace
 
+size_t FailingSettingsStorage::GetBytesInUse() {
+  // Let SettingsStorageQuotaEnforcer implement this.
+  NOTREACHED() << "Not implemented";
+  return 0;
+}
+
 SettingsStorage::ReadResult FailingSettingsStorage::Get(
     const std::string& key) {
   return ReadResultError();
 }
 
 SettingsStorage::ReadResult FailingSettingsStorage::Get(
     const std::vector<std::string>& keys) {
   return ReadResultError();
 }
 
@@ skipping 19 matching lines @@
 SettingsStorage::WriteResult FailingSettingsStorage::Remove(
     const std::vector<std::string>& keys) {
   return WriteResultError();
 }
 
 SettingsStorage::WriteResult FailingSettingsStorage::Clear() {
   return WriteResultError();
 }
 
 }  // namespace extensions