Implement MediaSession (metadata) per frame [NOT READY, HAS DEPENDENCY]

content/renderer/media/android/renderer_media_session_manager.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 "content/renderer/media/android/renderer_media_session_manager.h"
 
 #include "base/logging.h"
 #include "base/optional.h"
 #include "content/common/media/media_metadata_sanitizer.h"
 #include "content/common/media/media_session_messages_android.h"
 #include "content/public/common/media_metadata.h"
+#include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/renderer/media/android/webmediasession_android.h"
+#include "third_party/WebKit/public/web/WebLocalFrame.h"
 
 namespace content {
 
 RendererMediaSessionManager::RendererMediaSessionManager(
     RenderFrame* render_frame)
     : RenderFrameObserver(render_frame),
       next_session_id_(blink::WebMediaSession::DefaultID + 1) {}
 
 RendererMediaSessionManager::~RendererMediaSessionManager() {
-  DCHECK(sessions_.empty())

[whywhat, 2016/09/13 16:23:26]

why removing this? no longer true?

[Zhiqiang Zhang (Slow), 2016/09/13 17:27:29]

It was even not true before this patch.
blink::MediaSession has a unique_ptr<> pointing at WebMediaSession.
WebMediaSession unregisters itself in the dtor.
Since blink::MediaSession is gc'ed, it is quite likely that
RenderMediaSessionManager is destroyed and WebMediaSession is still alive,
hitting this DCHECK.

To trigger it, just go to the MediaSession test page, play the audio, and
navigate to another URL.

-      << "RendererMediaSessionManager is owned by RenderFrameImpl and is "
-         "destroyed only after all media sessions are destroyed.";
 }
 
 bool RendererMediaSessionManager::OnMessageReceived(const IPC::Message& msg) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(RendererMediaSessionManager, msg)
     IPC_MESSAGE_HANDLER(MediaSessionMsg_DidActivate, OnDidActivate)
     IPC_MESSAGE_HANDLER(MediaSessionMsg_DidDeactivate, OnDidDeactivate)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ skipping 23 matching lines @@
 void RendererMediaSessionManager::Deactivate(
     int session_id,
     std::unique_ptr<blink::WebMediaSessionDeactivateCallback> callback) {
   int request_id = pending_deactivation_requests_.Add(callback.release());
   Send(
       new MediaSessionHostMsg_Deactivate(routing_id(), session_id, request_id));
 }
 
 void RendererMediaSessionManager::SetMetadata(
     int session_id, const base::Optional<MediaMetadata>& metadata) {
+  // Non-MainFrames will be ignored.
+  if (render_frame()->GetWebFrame()->parent())
+    return;

[whywhat, 2016/09/13 16:23:26]

print a message here too?
are we 100% sure GetWebFrame() never returns null?

[Zhiqiang Zhang (Slow), 2016/09/13 18:51:52]

Seems not 100%. Fixed.

 
   // TODO(zqzhang): print a console warning when metadata is dirty. See
   // https://crbug.com/625244.
   Send(new MediaSessionHostMsg_SetMetadata(
       routing_id(), session_id,
       (!metadata.has_value() ||
        MediaMetadataSanitizer::CheckSanity(metadata.value()))
           ? metadata
           : MediaMetadataSanitizer::Sanitize(metadata.value())));
 }
@@ skipping 11 matching lines @@
   pending_activation_requests_.Remove(request_id);
 }
 
 void RendererMediaSessionManager::OnDidDeactivate(int request_id) {
   DCHECK(pending_deactivation_requests_.Lookup(request_id)) << request_id;
   pending_deactivation_requests_.Lookup(request_id)->onSuccess();
   pending_deactivation_requests_.Remove(request_id);
 }
 
 }  // namespace content