Decouple MediaSession messages from WebContents (full patch)

content/browser/media/session/media_session_android.h

+// Copyright 2016 The Chromium Authors. All rights reserved.

[Zhiqiang Zhang (Slow), 2016/10/26 12:50:37]

This is a hybrid of "WebContentsAndroid & WebContentsObserverProxy" for
MediaSession. Used for communicating between native and Java.

+// 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_ANDROID_H_
+#define CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_ANDROID_H_
+
+#include <jni.h>
+#include <memory>
+#include <vector>
+
+#include "base/android/scoped_java_ref.h"
+#include "content/public/browser/media_session_observer.h"
+
+namespace content {
+
+class MediaSessionImpl;
+
+bool RegisterMediaSessionNatives(JNIEnv* env);
+
+// This class is interlayer between native MediaSession and Java
+// MediaSession. This class is owned by the native MediaSession and will
+// teardown Java MediaSession when the native MediaSession is destroyed.
+// Java MediaSessionObservers are also proxied via this class.
+class MediaSessionAndroid final : public MediaSessionObserver {
+ public:
+  MediaSessionAndroid(MediaSession* session);

[jam, 2016/10/26 17:30:59]

nit: explicit

[Zhiqiang Zhang (Slow), 2016/10/26 18:44:25]

Done in the splitted CL.

+  ~MediaSessionAndroid() override;
+
+  static bool Register(JNIEnv* env);
+
+  base::android::ScopedJavaLocalRef<jobject> GetJavaSession();
+
+  // MediaSessionObserver implementation.
+  void MediaSessionDestroyed() override;
+  void MediaSessionStateChanged(bool is_controllable,
+                                bool is_suspended) override;
+  void MediaSessionMetadataChanged(
+      const base::Optional<MediaMetadata>& metadata) override;
+
+  // MediaSession method wrappers.
+  void Resume(JNIEnv* env, const base::android::JavaParamRef<jobject>& j_obj);
+  void Suspend(JNIEnv* env, const base::android::JavaParamRef<jobject>& j_obj);
+  void Stop(JNIEnv* env, const base::android::JavaParamRef<jobject>& j_obj);
+
+ private:
+  // The linked Java object
+  base::android::ScopedJavaGlobalRef<jobject> j_media_session_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaSessionAndroid);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEDIA_SESSION_MEDIA_SESSION_ANDROID_H_