Force MimeHandlerView to always use BrowserPlugin

content/browser/frame_host/render_widget_host_view_child_frame.cc

Index: content/browser/frame_host/render_widget_host_view_child_frame.cc
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.cc b/content/browser/frame_host/render_widget_host_view_child_frame.cc
index ed316e45611a80bd7fdb1c84c13a64e86d009e9d..f283befd6a8139cdc31a5687463a1bfa2b9d8100 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.cc
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.cc
@@ -199,7 +199,12 @@ gfx::Vector2dF RenderWidgetHostViewChildFrame::GetLastScrollOffset() const {
 }
 
 gfx::NativeView RenderWidgetHostViewChildFrame::GetNativeView() const {
-  NOTREACHED();
+  // TODO(ekaramad): To accomodate MimeHandlerViewGuest while embedded inside
+  // OOPIF-webview, we need to return the native view to be used by
+  // RenderWidgetHostViewGuest. Remove this once https://crbug.com/642826 is
+  // fixed.
+  if (frame_connector_)
+    return frame_connector_->GetParentRenderWidgetHostView()->GetNativeView();
   return nullptr;
 }