Populates sourceDevice attribute into TouchEvent

Source/core/input/InputDevice.cpp

 // 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 "config.h"
 #include "core/input/InputDevice.h"
 
 namespace blink {
 
 InputDevice::InputDevice(bool firesTouchEvents)
 {
     m_firesTouchEvents = firesTouchEvents;
 }
 
 InputDevice::InputDevice(const InputDeviceInit& initializer)
 {
     m_firesTouchEvents = initializer.firesTouchEvents();
 }
 
 InputDevice::~InputDevice()
 {
 }
 
+InputDevice* InputDevice::touchEventInstance()
+{
+    DEFINE_STATIC_LOCAL(Persistent<InputDevice>, instance, (InputDevice::create(true)));
+    return instance;
+}
+
 } // namespace blink