[MediaRouter] The minimal change to make everything build on Android.

chrome/browser/media/router/media_router_dialog_controller.h

+// 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.
+
+#ifndef CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_H_
+#define CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/media/router/create_session_request.h"
+
+namespace content {
+class WebContents;
+}  // namespace content
+
+namespace media_router {
+
+// An implementation of this interface is tied to a WebContents known as the
+// initiator, and is lazily created when a Media Router dialog needs to be
+// shown. The MediaRouterDialogController allows creating, querying, and
+// removing a Media Router dialog modal to the initiator WebContents.
+// This class is not thread safe and must be called on the UI thread.
+class MediaRouterDialogController {
+ public:
+  ~MediaRouterDialogController() = default;

[imcheng, 2015/07/13 22:04:14]

Does this need to be virtual?

[whywhat, 2015/07/15 12:41:04]

Done.

+
+  // Gets a reference to the MediaRouterDialogController associated with
+  // |web_contents|, creating one if it does not exist. The returned pointer is
+  // guaranteed to be non-null.
+  static MediaRouterDialogController* GetOrCreateForWebContents(

[imcheng, 2015/07/13 22:04:14]

I see that for MediaRouterFactory we return either the desktop or Android
version with #ifdefs. Can we do the same for MRDC so we don't have multiple
definitions of this function across files?

[whywhat, 2015/07/15 12:41:04]

Are you saying you prefer a clear ifdef in one file to conditional linking (by
including one or another cc file in the build)?
I'll look into that.

[imcheng, 2015/07/16 18:28:19]

Yeah. I was thinking we can put the definition in
media_router_dialog_controller.cc.

+      content::WebContents* web_contents);
+
+  // Creates a Media Router modal dialog using the initiator and parameters
+  // specified in |request|. If the dialog already exists, brings the dialog
+  // to the front, but does not change the dialog with |request|.
+  // Returns WebContents for the media router dialog if a dialog was created.

[imcheng, 2015/07/13 22:04:14]

s/WebContents for the media router dialog/true ? Similarly for below

[whywhat, 2015/07/15 12:41:04]

Done.

+  // Otherwise returns nullptr and |request| is deleted.
+  virtual bool ShowMediaRouterDialogForPresentation(
+      scoped_ptr<CreateSessionRequest> request) = 0;
+};
+
+}  // namespace media_router
+
+#endif  // CHROME_BROWSER_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_H_