use enum to specify deviceSource for fling animation.

content/renderer/render_widget_fullscreen_pepper.cc

Index: content/renderer/render_widget_fullscreen_pepper.cc
diff --git a/content/renderer/render_widget_fullscreen_pepper.cc b/content/renderer/render_widget_fullscreen_pepper.cc
index 0fd430eb79f9dc73b43395c8e06061340ca1d14c..b101825621fe4b621cd024b9909875b9e2467468 100644
--- a/content/renderer/render_widget_fullscreen_pepper.cc
+++ b/content/renderer/render_widget_fullscreen_pepper.cc
@@ -75,7 +75,7 @@ WebMouseEvent WebMouseEventFromGestureEvent(const WebGestureEvent& gesture) {
       break;
 
     case WebInputEvent::GestureFlingStart:
-      if (gesture.sourceDevice == WebGestureEvent::Touchscreen) {
+      if (gesture.sourceDevice == blink::WebGestureDeviceTouchpad) {
         // A scroll gesture on the touchscreen may end with a GestureScrollEnd
         // when there is no velocity, or a GestureFlingStart when it has a
         // velocity. In both cases, it should end the drag that was initiated by