Make WindowAndroid a ViewAndroid

ui/android/window_android.cc

Index: ui/android/window_android.cc
diff --git a/ui/android/window_android.cc b/ui/android/window_android.cc
index 970ddd0415d12fa59ce06c5648f26e87c981b339..4bd0f4d665804fe8014703a8b8d4fab465bb79ce 100644
--- a/ui/android/window_android.cc
+++ b/ui/android/window_android.cc
@@ -36,6 +36,7 @@ bool WindowAndroid::RegisterWindowAndroid(JNIEnv* env) {
 }
 
 WindowAndroid::~WindowAndroid() {
+  DCHECK(parent_ == nullptr) << "WindowAndroid must be a root view.";
   DCHECK(!compositor_);
 }
 
@@ -142,6 +143,11 @@ bool WindowAndroid::CanRequestPermission(const std::string& permission) {
       base::android::ConvertUTF8ToJavaString(env, permission).obj());
 }
 
+WindowAndroid* WindowAndroid::GetWindowAndroid() {
+  DCHECK(parent_ == nullptr);
+  return this;
+}
+
 // ----------------------------------------------------------------------------
 // Native JNI methods
 // ----------------------------------------------------------------------------