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

chrome/browser/extensions/settings/settings_api.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/settings_api.h"
 
 #include "base/bind.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extensions_quota_service.h"
 #include "chrome/browser/extensions/settings/settings_api.h"
@@ skipping 214 matching lines @@
 bool ClearSettingsFunction::RunWithStorage(SettingsStorage* storage) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   return UseWriteResult(storage->Clear());
 }
 
 void ClearSettingsFunction::GetQuotaLimitHeuristics(
     QuotaLimitHeuristics* heuristics) const {
   GetModificationQuotaLimitHeuristics(heuristics);
 }
 
+bool GetBytesInUseSettingsFunction::RunWithStorage(SettingsStorage* storage) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  result_.reset(Value::CreateIntegerValue(storage->GetBytesInUse()));
+  return true;
+}
+
 }  // namespace extensions