Disable direct routing of mouse events for RenderWidgetHostViewGuest

content/browser/renderer_host/render_widget_host_input_event_router.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_input_event_router.h"
 
 #include <vector>
 
 #include "base/metrics/histogram_macros.h"
 
@@ skipping 174 matching lines @@
     target = mouse_capture_target_.target;
     transformed_point = root_view->TransformPointToCoordSpaceForView(
         gfx::Point(event->x, event->y), target);
     if (event->type == blink::WebInputEvent::MouseUp)
       mouse_capture_target_.target = nullptr;
   } else {
     target = FindEventTarget(root_view, gfx::Point(event->x, event->y),
                              &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;
 
   if (!target)
     return;
 
   // SendMouseEnterOrLeaveEvents is called with the original event
   // coordinates, which are transformed independently for each view that will
   // receive an event.
   if ((event->type == blink::WebInputEvent::MouseLeave ||
@@ skipping 506 matching lines @@
   if (!touchpad_gesture_target_.target)
     return;
 
   // TODO(mohsen): Add tests to check event location.
   event->x += touchpad_gesture_target_.delta.x();
   event->y += touchpad_gesture_target_.delta.y();
   touchpad_gesture_target_.target->ProcessGestureEvent(*event, latency);
 }
 
 }  // namespace content