Make MediaSession a runtime-enabled feature on Desktop.

content/browser/media/session/media_session_delegate_android.h

+// 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.
+
+#ifndef CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_DELEGATE_ANDROID_H_
+#define CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_DELEGATE_ANDROID_H_
+
+#include <jni.h>
+
+#include "base/android/scoped_java_ref.h"
+#include "content/browser/media/session/media_session_delegate.h"
+
+namespace content {
+
+// MediaSessionDelegateAndroid handles the audio focus at a system level on
+// Android. It is also proxying the JNI calls.
+class MediaSessionDelegateAndroid : public MediaSessionDelegate {
+ public:
+  static bool Register(JNIEnv* env);
+
+  explicit MediaSessionDelegateAndroid(MediaSession* media_session);
+
+  void Initialize();
+
+  bool RequestAudioFocus(MediaSession::Type type) override;
+  void AbandonAudioFocus() override;
+
+  // Called when the Android system requests the MediaSession to be suspended.
+  // Called by Java through JNI.
+  void OnSuspend(JNIEnv* env,
+                 const base::android::JavaParamRef<jobject>& obj,
+                 jboolean temporary);
+
+  // Called when the Android system requests the MediaSession to be resumed.
+  // Called by Java through JNI.
+  void OnResume(JNIEnv* env, const base::android::JavaParamRef<jobject>& obj);
+
+  // Called when the Android system requests the MediaSession to duck.
+  // Called by Java through JNI.
+  void OnSetVolumeMultiplier(JNIEnv* env, jobject obj,
+                             jdouble volume_multiplier);
+
+  // Called when the Android system requests the MediaSession to duck.
+  // Called by Java through JNI.
+  void RecordSessionDuck(JNIEnv* env,
+                         const base::android::JavaParamRef<jobject> &obj);
+
+ private:
+  // Weak pointer because |this| is owned by |media_session_|.
+  MediaSession* media_session_;
+  base::android::ScopedJavaGlobalRef<jobject> j_media_session_delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaSessionDelegateAndroid);
+};
+
+}  // namespace content
+
+#endif // CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_DELEGATE_ANDROID_H_