mash: Fix DCHECK when clicking on window close box

mash/wm/frame/move_event_handler.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 "mash/wm/frame/move_event_handler.h"
 
 #include "components/mus/public/cpp/window.h"
 #include "components/mus/public/interfaces/cursor.mojom.h"
 #include "mash/wm/frame/move_loop.h"
 #include "mojo/converters/input_events/input_events_type_converters.h"
@@ skipping 40 matching lines @@
 }
 
 MoveEventHandler::~MoveEventHandler() {
   Detach();
 }
 
 void MoveEventHandler::ProcessLocatedEvent(ui::LocatedEvent* event) {
   const bool had_move_loop = move_loop_.get() != nullptr;
   DCHECK(event->IsMouseEvent() || event->IsTouchEvent());
 
+  // This event handler can receive mouse events like ET_MOUSE_CAPTURE_CHANGED
+  // that cannot be converted to PointerEvents. Ignore them because they aren't
+  // needed for move handling.
+  if (!ui::PointerEvent::CanConvertFrom(*event))
+    return;
+
   // TODO(moshayedi): no need for this once MoveEventHandler directly receives
   // pointer events.
   scoped_ptr<ui::PointerEvent> pointer_event;
   if (event->IsMouseEvent())
     pointer_event.reset(new ui::PointerEvent(*event->AsMouseEvent()));
   else
     pointer_event.reset(new ui::PointerEvent(*event->AsTouchEvent()));
 
   if (move_loop_) {
     if (move_loop_->Move(*pointer_event.get()) == MoveLoop::DONE)
@@ skipping 43 matching lines @@
   event->SetHandled();
 }
 
 void MoveEventHandler::OnWindowDestroying(aura::Window* window) {
   DCHECK_EQ(root_window_, window);
   Detach();
 }
 
 }  // namespace wm
 }  // namespace mash