Allow MimeHandlerViewGuest be embedded inside OOPIFs

content/browser/renderer_host/render_widget_host_view_base.cc

Index: content/browser/renderer_host/render_widget_host_view_base.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_base.cc b/content/browser/renderer_host/render_widget_host_view_base.cc
index 955f0f97d111d46a7c6fc1f3b7a7219159bbf673..bea07a8a9e422048332e11716a16fdba56995b07 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.cc
+++ b/content/browser/renderer_host/render_widget_host_view_base.cc
@@ -463,6 +463,11 @@ bool RenderWidgetHostViewBase::IsRenderWidgetHostViewChildFrame() {
   return false;
 }
 
+RenderWidgetHostViewBase* RenderWidgetHostViewBase::GetOuterView() {
+  NOTREACHED();
+  return this;
+}
+
 void RenderWidgetHostViewBase::TextInputStateChanged(
     const TextInputState& text_input_state) {
 // TODO(ekaramad): Use TextInputManager code paths for IME on other platforms.