Revert of [Android] Stop hiding the RWHV layer subtree when hiding the widget

ui/android/window_android.cc

 // Copyright 2013 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.
 
 #include "ui/android/window_android.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_weak_ref.h"
 #include "base/android/scoped_java_ref.h"
@@ skipping 25 matching lines @@
 WindowAndroid::~WindowAndroid() {
   DCHECK(!compositor_);
 }
 
 void WindowAndroid::OnCompositingDidCommit() {
   FOR_EACH_OBSERVER(WindowAndroidObserver,
                     observer_list_,
                     OnCompositingDidCommit());
 }
 
-void WindowAndroid::OnVisibilityChanged(bool visible) {
-  FOR_EACH_OBSERVER(WindowAndroidObserver, observer_list_,
-                    OnRootWindowVisibilityChanged(visible));
-}
-
 void WindowAndroid::AddObserver(WindowAndroidObserver* observer) {
   if (!observer_list_.HasObserver(observer))
     observer_list_.AddObserver(observer);
 }
 
 void WindowAndroid::RemoveObserver(WindowAndroidObserver* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
 void WindowAndroid::AttachCompositor(WindowAndroidCompositor* compositor) {
@@ skipping 37 matching lines @@
   base::TimeDelta vsync_period(
       base::TimeDelta::FromMicroseconds(period_micros));
   FOR_EACH_OBSERVER(
       WindowAndroidObserver,
       observer_list_,
       OnVSync(frame_time, vsync_period));
   if (compositor_)
     compositor_->OnVSync(frame_time, vsync_period);
 }
 
-void WindowAndroid::OnActivityResumed(JNIEnv* env, jobject obj) {
-  FOR_EACH_OBSERVER(WindowAndroidObserver, observer_list_, OnActivityResumed());
-}
-
-void WindowAndroid::OnActivityPaused(JNIEnv* env, jobject obj) {
-  FOR_EACH_OBSERVER(WindowAndroidObserver, observer_list_, OnActivityPaused());
-}
-
 // ----------------------------------------------------------------------------
 // Native JNI methods
 // ----------------------------------------------------------------------------
 
 jlong Init(JNIEnv* env, jobject obj) {
   WindowAndroid* window = new WindowAndroid(env, obj);
   return reinterpret_cast<intptr_t>(window);
 }
 
 }  // namespace ui