Don't release capture when this window doesn't already have it

ui/views/win/hwnd_message_handler.cc

 // Copyright (c) 2012 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/views/win/hwnd_message_handler.h"
 
 #include <dwmapi.h>
 #include <shellapi.h>
 
 #include "base/bind.h"
@@ skipping 702 matching lines @@
 void HWNDMessageHandler::ClearNativeFocus() {
   ::SetFocus(hwnd());
 }
 
 void HWNDMessageHandler::SetCapture() {
   DCHECK(!HasCapture());
   ::SetCapture(hwnd());
 }
 
 void HWNDMessageHandler::ReleaseCapture() {
-  ::ReleaseCapture();
+  if (HasCapture())
+    ::ReleaseCapture();
 }
 
 bool HWNDMessageHandler::HasCapture() const {
   return ::GetCapture() == hwnd();
 }
 
 void HWNDMessageHandler::SetVisibilityChangedAnimationsEnabled(bool enabled) {
   if (base::win::GetVersion() >= base::win::VERSION_VISTA) {
     int dwm_value = enabled ? FALSE : TRUE;
     DwmSetWindowAttribute(
@@ skipping 1373 matching lines @@
     DwmExtendFrameIntoClientArea(hwnd(), &m);
   }
   if (window_pos->flags & SWP_SHOWWINDOW)
     delegate_->HandleVisibilityChanged(true);
   else if (window_pos->flags & SWP_HIDEWINDOW)
     delegate_->HandleVisibilityChanged(false);
   SetMsgHandled(FALSE);
 }
 
 }  // namespace views