Implement an initial extension settings API.

chrome/browser/extensions/extension_settings_noop_storage.cc

+// Copyright (c) 2011 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/extension_settings_noop_storage.h"
+
+#include "base/bind.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/message_loop.h"
+#include "base/task.h"
+
+namespace {
+
+// Calls OnSuccess() of a callback with settings, after posting back to the UI
+// thread.
+class SuccessResultClosure {

[Matt Perry, 2011/06/23 19:14:11]

it seems like a closure class is unnecessary here. you could do the same with a
simple static function:

static CallOnSuccess(ExtensionSettingsStorage::Callback* callback,
DictionaryValue* settings) {
  callback->OnSuccess(settings);
  delete callback;
}

and use it like:
BrowserThread::PostTask(NewRunnableFunction(CallOnSuccess, callback, settings));

(or whatever the equivalent base::Bind() syntax is - that's newer and I'm not
familiar with it yet.)

[Matt Perry, 2011/06/23 19:14:11]

btw, in general, your use of closures is not a common pattern in chrome. more
often you'll just see code calling PostTask directly to a method of the current
class.

sometimes the closures are appropriate and likely result in less+cleaner code
(like your leveldb file), but in this case I think a simpler approach is better.

[not at google - send to devlin, 2011/06/27 08:51:02]

Done.

Yeah it all came from me not realising how easy it is to curry arguments to
functions with base::Bind.  Thanks.

+ public:
+  // Ownership of callback is taken.
+  SuccessResultClosure(
+      ExtensionSettingsStorage::Callback* callback, DictionaryValue* settings)
+      : callback_(callback), settings_(settings) {
+  }
+
+  ~SuccessResultClosure() {}
+
+  void Run() {
+    MessageLoop::current()->PostTask(
+        FROM_HERE,
+        base::Bind(&SuccessResultClosure::Run2, base::Unretained(this)));
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SuccessResultClosure);
+
+  void Run2() {
+    callback_->OnSuccess(settings_);
+    delete this;
+  }
+
+  scoped_ptr<ExtensionSettingsStorage::Callback> callback_;
+  DictionaryValue* settings_;
+};
+
+}  // namespace
+
+void ExtensionSettingsNoopStorage::Get(
+    const std::string& key, ExtensionSettingsStorage::Callback* callback) {
+  (new SuccessResultClosure(callback, new DictionaryValue()))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Get(
+    const ListValue& keys, ExtensionSettingsStorage::Callback* callback) {
+  (new SuccessResultClosure(callback, new DictionaryValue()))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Get(
+    ExtensionSettingsStorage::Callback* callback) {
+  (new SuccessResultClosure(callback, new DictionaryValue()))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Set(
+    const std::string& key,
+    const Value& value,
+    ExtensionSettingsStorage::Callback* callback) {
+  DictionaryValue* settings = new DictionaryValue();
+  settings->Set(key, value.DeepCopy());
+  (new SuccessResultClosure(callback, settings))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Set(
+    const DictionaryValue& values,
+    ExtensionSettingsStorage::Callback* callback) {
+  (new SuccessResultClosure(callback, values.DeepCopy()))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Remove(
+    const std::string& key, ExtensionSettingsStorage::Callback *callback) {
+  (new SuccessResultClosure(callback, new DictionaryValue()))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Remove(
+    const ListValue& keys, ExtensionSettingsStorage::Callback *callback) {
+  (new SuccessResultClosure(callback, new DictionaryValue()))->Run();
+}
+
+void ExtensionSettingsNoopStorage::Clear(
+    ExtensionSettingsStorage::Callback* callback) {
+  (new SuccessResultClosure(callback, new DictionaryValue()))->Run();
+}