Let CastMediaBlocker observe MediaSession instead of WebContents

chromecast/browser/cast_media_blocker.cc

 // Copyright 2016 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 "chromecast/browser/cast_media_blocker.h"
 
-#include "base/callback.h"
+#include "base/bind.h"
 #include "base/threading/thread_checker.h"
+#include "content/public/browser/media_session.h"
 #include "content/public/browser/web_contents.h"
 
 namespace chromecast {
 namespace shell {
 
-CastMediaBlocker::CastMediaBlocker(content::WebContents* web_contents)
+CastMediaBlocker::CastMediaBlocker(content::MediaSession* media_session)
     : CastMediaBlocker::CastMediaBlocker(
-          web_contents,
+          media_session,

[derekjchow1, 2016/10/24 18:50:33]

How is a content embedder supposed to obtain a reference to a MediaSession? For
Cast, we need to suspend media for a given WebContents. Is there a getter
function  in WebContents to obtain the MediaSession?

Similarily, is it expected there's a 1-1 mapping from MediaSession to
WebContents?

[Zhiqiang Zhang (Slow), 2016/10/28 10:36:52]

Yes, it is 1-1 mapping.
You can use MediaSession::Get(WebContents*).
It's in another CL which is under review.

           base::Bind(&CastMediaBlocker::Suspend, base::Unretained(this)),
           base::Bind(&CastMediaBlocker::Resume, base::Unretained(this))) {}

[Zhiqiang Zhang (Slow), 2016/10/24 18:29:32]

Are these callbacks used for testing?
After we expose MediaSession in content/public, you can let MediaSessionMock
derive from content::MediaSession and use EXPECT_CALL on the mock. Then these
callbacks can be removed.

[derekjchow1, 2016/10/24 18:50:33]

Correct. Your approach SGTM. We can probably remove these callback if there's a
MockMediaSession we can rely on.

[Zhiqiang Zhang (Slow), 2016/10/28 10:36:52]

Done removing the callbacks. See the tests for details :)

 
-CastMediaBlocker::CastMediaBlocker(content::WebContents* web_contents,
+CastMediaBlocker::CastMediaBlocker(content::MediaSession* media_session,
                                    const base::Closure& suspend_cb,
                                    const base::Closure& resume_cb)
-    : content::WebContentsObserver(web_contents),
+    : content::MediaSessionObserver(media_session),
       suspend_cb_(suspend_cb),
       resume_cb_(resume_cb),
       blocked_(false),
       paused_by_user_(true),
       suspended_(true),
       controllable_(false) {}
 
 CastMediaBlocker::~CastMediaBlocker() {}
 
 void CastMediaBlocker::BlockMediaLoading(bool blocked) {
@@ skipping 60 matching lines @@
         suspend_cb_.Run();
     }
 
     // If not blocking, cache the user's play intent.
     if (!blocked_)
       paused_by_user_ = suspended_;
   }
 }
 
 void CastMediaBlocker::Suspend() {
-  if (!web_contents())
+  if (!media_session())
     return;
 
   LOG(INFO) << "Suspending media session.";
-  web_contents()->SuspendMediaSession();
+  media_session()->Suspend(content::MediaSession::SuspendType::SYSTEM);
 }
 
 void CastMediaBlocker::Resume() {
-  if (!web_contents())
+  if (!media_session())
     return;
 
   LOG(INFO) << "Resuming media session.";
-  web_contents()->ResumeMediaSession();
+  media_session()->Resume(content::MediaSession::SuspendType::SYSTEM);
 }
 
 }  // namespace shell
 }  // namespace chromecast