Disable direct routing of mouse events for RenderWidgetHostViewGuest

content/browser/renderer_host/render_widget_host_input_event_router.cc

Index: content/browser/renderer_host/render_widget_host_input_event_router.cc
diff --git a/content/browser/renderer_host/render_widget_host_input_event_router.cc b/content/browser/renderer_host/render_widget_host_input_event_router.cc
index 68b19afed29ace6e202658fbb5c6eb2ea06a19c2..8ad60fe3b5955a94014e2741ac3067d6e121e4b8 100644
--- a/content/browser/renderer_host/render_widget_host_input_event_router.cc
+++ b/content/browser/renderer_host/render_widget_host_input_event_router.cc
@@ -192,6 +192,14 @@ void RenderWidgetHostInputEventRouter::RouteMouseEvent(
                              &transformed_point);
   }
 
+  // RenderWidgetHostViewGuest does not properly handle direct routing of mouse
+  // events, so they have to go by the double-hop forwarding path through
+  // the embedding renderer and then BrowserPluginGuest.
+  if (target && target->IsRenderWidgetHostViewGuest()) {
+    root_view->ProcessMouseEvent(*event, latency);

[wjmaclean, 2016/09/21 18:34:52]

Do we always want to go to the root? This will work in most cases, but could we
have a WebView embedded in a cross-site iframe? If that doesn't happen, then
this is fine.

[kenrb, 2016/09/21 18:56:36]

WebViews can't be embedded by web content, so AFAIK this should be okay.

+    return;
+  }
+
   if (event->type == blink::WebInputEvent::MouseDown)
     mouse_capture_target_.target = target;