Link MediaSessionTabHelper with native MediaSession [CL is going to be split]

content/public/android/java/src/org/chromium/content_public/browser/MediaSessionDelegate.java

+// 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.
+
+package org.chromium.content_public.browser;
+
+import org.chromium.content_public.common.MediaMetadata;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+@JNINamespace("content")
+public class MediaSessionDelegate {
+
+    private long mNativeMediaSessionDelegateAndroid;
+
+    public boolean hasNativeMediaSession() {

[boliu, 2016/10/19 20:39:40]

private?

[Zhiqiang Zhang (Slow), 2016/10/20 16:22:32]

Done.

+        return mNativeMediaSessionDelegateAndroid != 0;
+    }
+
+    public void unlinkMediaSession() {
+        if (hasNativeMediaSession())

[boliu, 2016/10/19 20:39:40]

nit: need braces

[Zhiqiang Zhang (Slow), 2016/10/20 16:22:32]

Done.

+            nativeUnlinkMediaSession(mNativeMediaSessionDelegateAndroid);
+    }
+
+    @CalledByNative
+    private void mediaSessionConnected(long nativeMediaSessionDelegateAndroid) {
+        mNativeMediaSessionDelegateAndroid = nativeMediaSessionDelegateAndroid;
+    }
+
+    @CalledByNative
+    public void mediaSessionDisconnected() {
+        mNativeMediaSessionDelegateAndroid = 0;
+    }
+
+    @CalledByNative
+    public void mediaSessionStateChanged(boolean isControllable, boolean isSuspended) {}
+
+    @CalledByNative
+    public void mediaSessionMetadataChanged(MediaMetadata metadata) {}
+
+    public void resumeMediaSession() {}

[boliu, 2016/10/19 20:39:40]

are these supposed to call into native?

[Zhiqiang Zhang (Slow), 2016/10/20 16:22:32]

Yes. Added javadoc.

+    public void suspendMediaSession() {}
+    public void stopMediaSession() {}
+
+    private native void nativeResumeMediaSession(long nativeMediaSessionDelegateAndroid);
+    private native void nativeSuspendMediaSession(long nativeMediaSessionDelegateAndroid);
+    private native void nativeStopMediaSession(long nativeMediaSessionDelegateAndroid);
+    private native void nativeUnlinkMediaSession(long nativeMediaSessionDelegateAndroid);
+}