Implement new compositor and ContentViewCore reparenting for VR Shell.

content/browser/android/content_view_core_impl.cc

Index: content/browser/android/content_view_core_impl.cc
diff --git a/content/browser/android/content_view_core_impl.cc b/content/browser/android/content_view_core_impl.cc
index e627fcd7611712cccc0a78f09b97a433a233f072..84cc6b1797b20ae385a845a2d56ea00c0d60faf3 100644
--- a/content/browser/android/content_view_core_impl.cc
+++ b/content/browser/android/content_view_core_impl.cc
@@ -275,19 +275,17 @@ void ContentViewCoreImpl::UpdateWindowAndroid(
     JNIEnv* env,
     const base::android::JavaParamRef<jobject>& obj,
     jlong window_android) {
+  if (!window_android || view_.GetWindowAndroid()) {
+    FOR_EACH_OBSERVER(ContentViewCoreImplObserver, observer_list_,
+                      OnDetachedFromWindow());
+    view_.RemoveFromParent();
+  }
   if (window_android) {
-    DCHECK(!view_.GetWindowAndroid());
     ui::WindowAndroid* window =
         reinterpret_cast<ui::WindowAndroid*>(window_android);
     window->AddChild(&view_);
-    FOR_EACH_OBSERVER(ContentViewCoreImplObserver,
-                      observer_list_,
+    FOR_EACH_OBSERVER(ContentViewCoreImplObserver, observer_list_,
                       OnAttachedToWindow());
-  } else {
-    FOR_EACH_OBSERVER(ContentViewCoreImplObserver,
-                      observer_list_,
-                      OnDetachedFromWindow());
-    view_.RemoveFromParent();
   }
 }