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 a0e03e50e2b4c1e66af709659cfc08a86e26b0ac..142aa2270c765a2697db3bd4cd83b56c150bd929 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.cc
+++ b/content/browser/renderer_host/render_widget_host_view_base.cc
@@ -464,6 +464,11 @@ bool RenderWidgetHostViewBase::IsRenderWidgetHostViewChildFrame() {
   return false;
 }
 
+RenderWidgetHostViewBase* RenderWidgetHostViewBase::GetEmbedderView() {
+  NOTREACHED();
+  return this;
+}
+
 void RenderWidgetHostViewBase::TextInputStateChanged(
     const TextInputState& text_input_state) {
 // TODO(ekaramad): Use TextInputManager code paths for IME on other platforms.