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

content/public/android/BUILD.gn

Index: content/public/android/BUILD.gn
diff --git a/content/public/android/BUILD.gn b/content/public/android/BUILD.gn
index 2633cb5e7f440207fa32c4578541aa2d0d98db45..99994034ad0f526506c686c3c14ecf8db4eee015 100644
--- a/content/public/android/BUILD.gn
+++ b/content/public/android/BUILD.gn
@@ -118,6 +118,7 @@ android_library("content_java") {
     "java/src/org/chromium/content/browser/ContentViewRenderView.java",
     "java/src/org/chromium/content/browser/ContentViewStatics.java",
     "java/src/org/chromium/content/browser/ContextualSearchClient.java",
+    "java/src/org/chromium/content/browser/ChromeMediaSession.java",
     "java/src/org/chromium/content/browser/DeviceSensors.java",
     "java/src/org/chromium/content/browser/DeviceUtils.java",
     "java/src/org/chromium/content/browser/FloatingWebActionModeCallback.java",
@@ -125,6 +126,7 @@ android_library("content_java") {
     "java/src/org/chromium/content/browser/InterstitialPageDelegateAndroid.java",
     "java/src/org/chromium/content/browser/JavascriptInterface.java",
     "java/src/org/chromium/content/browser/MediaResourceGetter.java",
+    "java/src/org/chromium/content/browser/MediaSessionObserver.java",
     "java/src/org/chromium/content/browser/MediaThrottler.java",
     "java/src/org/chromium/content/browser/MemoryMonitorAndroid.java",
     "java/src/org/chromium/content/browser/MotionEventSynthesizer.java",
@@ -299,6 +301,7 @@ generate_jni("content_jni_headers") {
     "java/src/org/chromium/content/browser/BackgroundSyncNetworkObserver.java",
     "java/src/org/chromium/content/browser/BrowserStartupController.java",
     "java/src/org/chromium/content/browser/ChildProcessLauncher.java",
+    "java/src/org/chromium/content/browser/ChromeMediaSession.java",
     "java/src/org/chromium/content/browser/ContentVideoView.java",
     "java/src/org/chromium/content/browser/ContentViewCore.java",
     "java/src/org/chromium/content/browser/ContentViewRenderView.java",