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

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

Index: content/public/android/java/src/org/chromium/content_public/browser/WebContentsObserver.java
diff --git a/content/public/android/java/src/org/chromium/content_public/browser/WebContentsObserver.java b/content/public/android/java/src/org/chromium/content_public/browser/WebContentsObserver.java
index 5dd8096fe2b16e97b4037eb895b5a35d19ed187c..3cb599f675f0e96d92388ac459f1b40b31d28cf3 100644
--- a/content/public/android/java/src/org/chromium/content_public/browser/WebContentsObserver.java
+++ b/content/public/android/java/src/org/chromium/content_public/browser/WebContentsObserver.java
@@ -4,8 +4,6 @@
 
 package org.chromium.content_public.browser;
 
-import org.chromium.content_public.common.MediaMetadata;
-
 import java.lang.ref.WeakReference;
 
 /**
@@ -173,19 +171,6 @@ public abstract class WebContentsObserver {
     public void didStartNavigationToPendingEntry(String url) {}
 
     /**
-     * Called when the media session state changed.
-     * @param isControllable if the session can be resumed or suspended.
-     * @param isSuspended if the session currently suspended or not.
-     */
-    public void mediaSessionStateChanged(boolean isControllable, boolean isSuspended) {}
-
-    /**
-     * Called when the media session metadata changed.
-     * @param metadata the new MediaMetadata after change.
-     */
-    public void mediaSessionMetadataChanged(MediaMetadata metadata) {}
-
-    /**
      * Stop observing the web contents and clean up associated references.
      */
     public void destroy() {