Refactor FileBasedPolicyProvider, introduce AsynchronousPolicyProvider.

chrome/browser/policy/asynchronous_policy_loader.cc

+// Copyright (c) 2010 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/policy/asynchronous_policy_loader.h"
+
+#include "base/message_loop.h"
+#include "base/task.h"
+#include "chrome/browser/browser_thread.h"
+
+namespace policy {
+
+AsynchronousPolicyLoader::AsynchronousPolicyLoader(
+    AsynchronousPolicyProvider::Delegate* delegate)
+    : delegate_(delegate),
+      origin_loop_(MessageLoop::current()) {}

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

Move closing brace to next line for scanability :)

[danno, 2010/12/06 14:05:12]

Actually, in my readability review, my reviewer suggested being consistent
everywhere with null bodies, recommending {} over {\n}. In headers {} is used
frequently. So, upshot: I'm not sure that I agree that adding the newline makes
it more readable.

+
+void AsynchronousPolicyLoader::Init() {
+  policy_.reset(delegate_->Load());
+}
+
+void AsynchronousPolicyLoader::Stop() {
+  DCHECK_EQ(MessageLoop::current(), origin_loop_);
+  delegate_.reset();
+}
+
+void AsynchronousPolicyLoader::SetProvider(
+    base::WeakPtr<AsynchronousPolicyProvider> provider) {
+  provider_ = provider;
+}
+
+// Manages the life cycle of a new policy while is pending on the message

[Mattias Nissler (ping if slow), 2010/12/06 10:26:20]

What is pending?

[danno, 2010/12/06 14:05:12]

Done.

+// loop waiting to be updated.
+class UpdatePolicyTask : public Task {
+ public:
+  UpdatePolicyTask(scoped_refptr<AsynchronousPolicyLoader> loader,
+                   DictionaryValue* new_policy)
+      : loader_(loader),
+        new_policy_(new_policy) {}
+
+  virtual void Run() {
+    loader_->UpdatePolicy(new_policy_.release());
+  }
+
+ private:
+  scoped_refptr<AsynchronousPolicyLoader> loader_;
+  scoped_ptr<DictionaryValue> new_policy_;
+  DISALLOW_COPY_AND_ASSIGN(UpdatePolicyTask);
+};
+
+void AsynchronousPolicyLoader::Reload() {
+  if (delegate_.get()) {
+    DictionaryValue* new_policy = delegate_->Load();
+    PostUpdatePolicyTask(new_policy);
+  }
+}
+
+void AsynchronousPolicyLoader::PostUpdatePolicyTask(
+    DictionaryValue* new_policy) {
+  origin_loop_->PostTask(FROM_HERE, new UpdatePolicyTask(this, new_policy));
+}
+
+void AsynchronousPolicyLoader::UpdatePolicy(DictionaryValue* new_policy_raw) {
+  DCHECK(policy_.get());
+  if (!policy_->Equals(new_policy_raw)) {
+    policy_.reset(new_policy_raw);
+    // TODO(danno): Change the notification between the provider and the
+    // PrefStore into a notification mechanism, removing the need for the
+    // WeakPtr for the provider.
+    if (provider_.get())
+      provider_->NotifyStoreOfPolicyChange();
+  }
+}
+
+}  // namespace policy