Populates sourceDevice attribute into TouchEvent

Source/core/input/InputDevice.h

Index: Source/core/input/InputDevice.h
diff --git a/Source/core/input/InputDevice.h b/Source/core/input/InputDevice.h
index 244e5638ceaae3b3e167c6ee2c9fa4736b0eede0..80238f0e90978aac33bef5b6c73a371356c0f3d0 100644
--- a/Source/core/input/InputDevice.h
+++ b/Source/core/input/InputDevice.h
@@ -16,6 +16,10 @@ class CORE_EXPORT InputDevice : public GarbageCollectedFinalized<InputDevice>, p
 
 public:
     ~InputDevice();
+
+    // This return a static local InputDevice pointer which has firesTouchEvents set to be true.
+    static InputDevice* touchEventInstance();
+
     static InputDevice* create(bool firesTouchEvents)
     {
         return new InputDevice(firesTouchEvents);