Allow OOPIFs to capture mouse input while mouse button is held down

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 "base/metrics/histogram_macros.h"
 #include "cc/quads/surface_draw_quad.h"
 #include "cc/surfaces/surface_id_allocator.h"
 #include "cc/surfaces/surface_manager.h"
@@ skipping 129 matching lines @@
   // parent frame has not sent a new compositor frame since that happened.
   if (iter == owner_map_.end())
     return root_view;
 
   return iter->second;
 }
 
 void RenderWidgetHostInputEventRouter::RouteMouseEvent(
     RenderWidgetHostViewBase* root_view,
     blink::WebMouseEvent* event) {
+  RenderWidgetHostViewBase* target;
   gfx::Point transformed_point;
-  RenderWidgetHostViewBase* target = FindEventTarget(
-      root_view, gfx::Point(event->x, event->y), &transformed_point);
+  if (mouse_capture_target_.target &&
+      event->type != blink::WebInputEvent::MouseDown) {

[mustaq, 2016/09/13 16:57:15]

Please also check that event modifier has at least one of
{Left,Middle,Right}ButtonDown bits set, to make sure it's a real drag case.
Otherwise, dragging out-of-window & releasing would mean a hovering mouse is
still appear captured.

[kenrb, 2016/09/13 20:01:52]

Done.

+    target = mouse_capture_target_.target;
+    transformed_point = root_view->TransformPointToCoordSpaceForView(
+        gfx::Point(event->x, event->y), target);
+  } else {
+    target = FindEventTarget(root_view, gfx::Point(event->x, event->y),
+                             &transformed_point);
+  }
+
+  if (event->type == blink::WebInputEvent::MouseUp)
+    mouse_capture_target_.target = nullptr;

[mustaq, 2016/09/13 16:57:15]

Or perhaps add the check (mentioned above) here and move this |if| to before the
above |if|.

[kenrb, 2016/09/13 20:01:53]

I have fixed this according to my current understanding of correctness. Mouse
capture now requires that either a ButtonDown modifier is set, or the event is a
MouseUp (I think we still want the capturing frame to get the MouseUp).

+  else if (event->type == blink::WebInputEvent::MouseDown)
+    mouse_capture_target_.target = target;
+
   if (!target)
     return;
 
   event->x = transformed_point.x();
   event->y = transformed_point.y();
   // TODO(wjmaclean): Initialize latency info correctly for OOPIFs.
   // https://crbug.com/613628
   ui::LatencyInfo latency_info;
   target->ProcessMouseEvent(*event, latency_info);
 }
@@ skipping 386 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