[MediaSession,Android] Request audio focus if needed when resuming playback from UI

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/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 110 matching lines @@
   if (audio_focus_state_ != State::SUSPENDED)
     return;
 
   OnResumeInternal(SuspendType::SYSTEM);
   UpdateWebContents();
 }
 
 void MediaSession::Resume() {
   DCHECK(IsSuspended());
 
+  // Request audio focus again in case we lost it because another app started
+  // playing while the playback was paused.
+  audio_focus_state_ = RequestSystemAudioFocus(audio_focus_type_)
+                           ? State::ACTIVE
+                           : State::INACTIVE;
+  if (audio_focus_state_ != State::ACTIVE)
+    return;
+
   OnResumeInternal(SuspendType::UI);
 }
 
 void MediaSession::Suspend() {
   DCHECK(!IsSuspended());
 
   OnSuspendInternal(SuspendType::UI);
 }
 
 bool MediaSession::IsSuspended() const {
@@ skipping 80 matching lines @@
 
   audio_focus_state_ = State::INACTIVE;
   UpdateWebContents();
 }
 
 void MediaSession::UpdateWebContents() {
   static_cast<WebContentsImpl*>(web_contents())->OnMediaSessionStateChanged();
 }
 
 }  // namespace content