[Media Router] Add Media Router Mojo impl code.

chrome/browser/media/router/media_router_mojo_impl_factory.cc

+// Copyright 2015 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/media/router/media_router_mojo_impl_factory.h"
+
+#include "chrome/browser/media/router/media_router_mojo_impl.h"
+#include "components/keyed_service/content/browser_context_dependency_manager.h"
+#include "extensions/browser/process_manager_factory.h"
+
+using content::BrowserContext;
+
+namespace media_router {
+
+namespace {
+
+base::LazyInstance<MediaRouterMojoImplFactory> service_factory =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+// static
+MediaRouterMojoImpl* MediaRouterMojoImplFactory::GetApiForBrowserContext(
+    BrowserContext* context) {
+  DCHECK(context);
+
+  return static_cast<MediaRouterMojoImpl*>(
+      service_factory.Get().GetServiceForBrowserContext(context, true));
+}
+
+MediaRouterMojoImplFactory::MediaRouterMojoImplFactory()
+    : BrowserContextKeyedServiceFactory(
+          "MediaRouterMojoImpl",
+          BrowserContextDependencyManager::GetInstance()) {
+  // MediaRouterMojoImpl depends on ProcessManager.
+  DependsOn(extensions::ProcessManagerFactory::GetInstance());
+}
+
+MediaRouterMojoImplFactory::~MediaRouterMojoImplFactory() {
+}
+
+KeyedService* MediaRouterMojoImplFactory::BuildServiceInstanceFor(
+    BrowserContext* context) const {
+  return new MediaRouterMojoImpl();
+}
+
+BrowserContext* MediaRouterMojoImplFactory::GetBrowserContextToUse(
+    BrowserContext* context) const {
+  // If |context| is incognito, use it instead of the original non-incognito
+  // BrowserContext.

[xhwang, 2015/05/28 06:53:21]

I don't understand this comment. It seems we always just return the input
|context|?

[imcheng (use chromium acct), 2015/05/28 20:46:35]

I clarified the comments a bit. Let me know if it sounds better?

[xhwang, 2015/05/28 22:08:09]

Acknowledged.

+  return context;
+}
+
+}  // namespace media_router