Drag and drop cleans up touch sequences from the source window.

ui/aura/window_event_dispatcher.cc

Index: ui/aura/window_event_dispatcher.cc
diff --git a/ui/aura/window_event_dispatcher.cc b/ui/aura/window_event_dispatcher.cc
index d34ad330b94132a61b11b0bb623da676b972620a..53f20e23c4f0ec6a9ef5e0170c5f15e48123808d 100644
--- a/ui/aura/window_event_dispatcher.cc
+++ b/ui/aura/window_event_dispatcher.cc
@@ -528,10 +528,8 @@ bool WindowEventDispatcher::CanDispatchToConsumer(
   return (consumer_window && consumer_window->GetRootWindow() == window());
 }
 
-void WindowEventDispatcher::DispatchCancelTouchEvent(
-    ui::GestureConsumer* raw_input_consumer,
-    ui::TouchEvent* event) {
-  // The touchcancel event's location is based on the last known location of
+void WindowEventDispatcher::DispatchSyntheticTouchEvent(ui::TouchEvent* event) {
+  // The synthetic event's location is based on the last known location of
   // the pointer, in dips. OnEventFromSource expects events with co-ordinates
   // in raw pixels, so we convert back to raw pixels here.

[sadrul, 2016/05/11 16:12:17]

Can you add a DCHECK() here that |event->type()| is always |ET_TOUCH_CANCELED|?
If that assumption changes, it'd be good to explicitly verify if we want to do
that.

[tdresser, 2016/05/11 16:32:31]

Done.

   event->UpdateForRootTransform(host_->GetRootTransform());