Refactored SettingsFrontend and forwarding of calls to the backends.

chrome/browser/extensions/settings/managed_value_store_cache.h

+// 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.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_SETTINGS_MANAGED_VALUE_STORE_CACHE_H_
+#define CHROME_BROWSER_EXTENSIONS_SETTINGS_MANAGED_VALUE_STORE_CACHE_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "chrome/browser/extensions/settings/value_store_cache.h"
+
+class Profile;
+
+namespace extensions {
+
+// TODO(joaodasilva): this is a work in progress. http://crbug.com/108992
+class ManagedValueStoreCache : public ValueStoreCache {
+ public:
+  explicit ManagedValueStoreCache(Profile* profile);

[not at google - send to devlin, 2012/07/19 06:43:17]

Like I said can it just be given the policy-specific stuff it needs?

[Joao da Silva, 2012/07/19 11:26:04]

Done.

+  virtual ~ManagedValueStoreCache();
+
+  // ValueStoreCache implementation:
+
+  virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() const OVERRIDE;
+
+  virtual void RunWithValueStoreForExtension(
+      const StorageCallback& callback,
+      scoped_refptr<const Extension> extension) OVERRIDE;

[not at google - send to devlin, 2012/07/19 06:43:17]

Does forcing this to be a scoped_refptr make sense when passing it into this
method? To me this implies that ownership passing into this method, which isn't
the case. const Extension* should be fine, implementations can hold onto it if
they want.

[Joao da Silva, 2012/07/19 11:26:04]

This method is invoked as an asynchronous callback, and the Extension might've
been unloaded in the UI thread by the time this executes on FILE, for example.
Not likely, but I think it's correct to make this a scoped_refptr in this case;
wdyt?

[not at google - send to devlin, 2012/07/19 12:29:52]

Ah I see. I just read through the base/bind related files was rather baffled
(it's very easy to read but very hard to understand), but base/callback explains
it; even if this method were to take a "const scoped_refptr&" the bound Callback
only holds onto the reference, not the object. So that wouldn't be safe either.

It's a very subtle implementation detail; could you add a comment in the header
file?

[Joao da Silva, 2012/07/19 13:17:51]

Yep, done.

+
+  virtual void DeleteStorageSoon(const std::string& extension_id) OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ManagedValueStoreCache);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_MANAGED_VALUE_STORE_CACHE_H_