[Android] A prototype of the interactive media notification.

content/browser/media/android/media_session.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/browser/media/android/media_session.h"
 
 #include "base/android/jni_android.h"
 #include "content/browser/media/android/media_session_observer.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "jni/MediaSession_jni.h"
 
 namespace content {
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(MediaSession);
 
 MediaSession::PlayerIdentifier::PlayerIdentifier(MediaSessionObserver* observer,
                                                  int player_id)
     : observer(observer),
       player_id(player_id) {
@@ skipping 53 matching lines @@
 
   if (audio_focus_state_ != State::Active)
     return false;
 
   // The session should be reset if a player is starting while all players are
   // suspended.
   if (old_audio_focus_state != State::Active)
     players_.clear();
 
   players_.insert(PlayerIdentifier(observer, player_id));
+  UpdateWebContents();
 
   return true;
 }
 
 void MediaSession::RemovePlayer(MediaSessionObserver* observer,
                                 int player_id) {
   auto it = players_.find(PlayerIdentifier(observer, player_id));
   if (it != players_.end())
     players_.erase(it);
 
   AbandonSystemAudioFocusIfNeeded();
 }
 
 void MediaSession::RemovePlayers(MediaSessionObserver* observer) {
   for (auto it = players_.begin(); it != players_.end();) {
     if (it->observer == observer)
       players_.erase(it++);
     else
       ++it;
   }
 
   AbandonSystemAudioFocusIfNeeded();
 }
 
 void MediaSession::OnSuspend(JNIEnv* env, jobject obj, jboolean temporary) {
-  OnSuspend(temporary);
+  OnSuspendInternal(temporary);
+  UpdateWebContents();
 }
 
 void MediaSession::OnResume(JNIEnv* env, jobject obj) {
-  OnResume();
+  OnResumeInternal();
+  UpdateWebContents();
+}
+
+void MediaSession::Resume() {
+  DCHECK(IsSuspended());
+
+  OnResumeInternal();
+}
+
+void MediaSession::Suspend() {
+  DCHECK(!IsSuspended());
+
+  // Since the playback can be resumed, it's a transient suspension.
+  OnSuspendInternal(true);
+}
+
+bool MediaSession::IsSuspended() const {
+  return audio_focus_state_ != State::Active;
+}
+
+bool MediaSession::IsControllable() const {
+  return audio_focus_state_ != State::Suspended &&

[Ted C, 2015/07/07 17:11:19]

Why does Suspended determine whether it is controllable?  Maybe that is just
unclear by the naming and at first glance, it being TemporarilySuspended doesn't
really clarify that was something that a user could have done.

Might be worth adding some documentation to the states to help the likes of me
understand this kind of implications in the future.

[whywhat, 2015/07/07 19:19:04]

So for the Content type, "Active" and "SuspendedTemporarily" states correspond
to playing and paused accordingly. "Suspended" means stopped.
I guess the terminology comes from the WebAudio's AudioContext. Mounir would
know better :)

+         audio_focus_type_ == Type::Content;
 }
 
 void MediaSession::ResetJavaRefForTest() {
   j_media_session_.Reset();
 }
 
 bool MediaSession::IsActiveForTest() const {
   return audio_focus_state_ == State::Active;
 }
 
 MediaSession::Type MediaSession::audio_focus_type_for_test() const {
   return audio_focus_type_;
 }
 
-void MediaSession::OnSuspend(bool temporary) {
+void MediaSession::RemoveAllPlayersForTest() {
+  players_.clear();
+  AbandonSystemAudioFocusIfNeeded();
+}
+
+void MediaSession::OnSuspendInternal(bool temporary) {
   if (temporary)
     audio_focus_state_ = State::TemporarilySuspended;
   else
     audio_focus_state_ = State::Suspended;
 
   for (const auto& it : players_)
     it.observer->OnSuspend(it.player_id);
 }
 
-void MediaSession::OnResume() {
+void MediaSession::OnResumeInternal() {
   audio_focus_state_ = State::Active;
 
   for (const auto& it : players_)
     it.observer->OnResume(it.player_id);
 }
 
 MediaSession::MediaSession(WebContents* web_contents)
     : WebContentsObserver(web_contents),
       audio_focus_state_(State::Suspended),
-      audio_focus_type_(Type::Transient) {
-}
+      audio_focus_type_(Type::Transient) {}
 
 void MediaSession::Initialize() {
   JNIEnv* env = base::android::AttachCurrentThread();
   DCHECK(env);
   j_media_session_.Reset(Java_MediaSession_createMediaSession(
       env,
       base::android::GetApplicationContext(),
       reinterpret_cast<intptr_t>(this)));
 }
 
@@ skipping 13 matching lines @@
     return;
 
   // During tests, j_media_session_ might be null.
   if (!j_media_session_.is_null()) {
     JNIEnv* env = base::android::AttachCurrentThread();
     DCHECK(env);
     Java_MediaSession_abandonAudioFocus(env, j_media_session_.obj());
   }
 
   audio_focus_state_ = State::Suspended;
+  UpdateWebContents();
+}
+
+void MediaSession::UpdateWebContents() {
+  web_contents()->OnMediaSessionStateChanged();
 }
 
 }  // namespace content