use enum to specify deviceSource for fling animation.

content/browser/renderer_host/input/touch_emulator.cc

Index: content/browser/renderer_host/input/touch_emulator.cc
diff --git a/content/browser/renderer_host/input/touch_emulator.cc b/content/browser/renderer_host/input/touch_emulator.cc
index bee97fb0772e38460e74df1bed6d03f01fc612c5..e66dcf9c87cfeee2412471bc6a3f50650a820088 100644
--- a/content/browser/renderer_host/input/touch_emulator.cc
+++ b/content/browser/renderer_host/input/touch_emulator.cc
@@ -319,7 +319,7 @@ void TouchEmulator::PinchEnd(const WebGestureEvent& event) {
 void TouchEmulator::FillPinchEvent(const WebInputEvent& event) {
   pinch_event_.timeStampSeconds = event.timeStampSeconds;
   pinch_event_.modifiers = event.modifiers;
-  pinch_event_.sourceDevice = blink::WebGestureEvent::Touchscreen;
+  pinch_event_.sourceDevice = blink::WebGestureDeviceTouchpad;
   pinch_event_.x = pinch_anchor_.x();
   pinch_event_.y = pinch_anchor_.y();
 }
@@ -328,7 +328,7 @@ void TouchEmulator::ScrollEnd(const WebGestureEvent& event) {
   WebGestureEvent scroll_event;
   scroll_event.timeStampSeconds = event.timeStampSeconds;
   scroll_event.modifiers = event.modifiers;
-  scroll_event.sourceDevice = blink::WebGestureEvent::Touchscreen;
+  scroll_event.sourceDevice = blink::WebGestureDeviceTouchpad;
   scroll_event.type = WebInputEvent::GestureScrollEnd;
   client_->ForwardGestureEvent(scroll_event);
 }