Dispatch a synthetic mouse exit to the widget handling mouse events when a widget grabs capture

ui/aura/window_tree_host.cc

 // Copyright (c) 2013 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 "ui/aura/window_tree_host.h"
 
 #include "base/debug/trace_event.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/env.h"
@@ skipping 132 matching lines @@
   // so just pass everything along to the host.
   SetCursorNative(cursor);
 }
 
 void WindowTreeHost::OnCursorVisibilityChanged(bool show) {
   // Clear any existing mouse hover effects when the cursor becomes invisible.
   // Note we do not need to dispatch a mouse enter when the cursor becomes
   // visible because that can only happen in response to a mouse event, which
   // will trigger its own mouse enter.
   if (!show) {
-    dispatcher()->DispatchMouseExitAtPoint(
+    ui::EventDispatchDetails details = dispatcher()->DispatchMouseExitAtPoint(
         dispatcher()->GetLastMouseLocationInRoot());
+    if (details.dispatcher_destroyed)
+      return;
   }
 
   OnCursorVisibilityChangedNative(show);
 }
 
 void WindowTreeHost::MoveCursorTo(const gfx::Point& location_in_dip) {
   gfx::Point host_location(location_in_dip);
   ConvertPointToHost(&host_location);
   MoveCursorToInternal(location_in_dip, host_location);
 }
@@ skipping 99 matching lines @@
   client::CursorClient* cursor_client = client::GetCursorClient(window());
   if (cursor_client) {
     const gfx::Display& display =
         gfx::Screen::GetScreenFor(window())->GetDisplayNearestWindow(window());
     cursor_client->SetDisplay(display);
   }
   dispatcher()->OnCursorMovedToRootLocation(root_location);
 }
 
 }  // namespace aura