use enum to specify deviceSource for fling animation

public/web/WebActiveWheelFlingParameters.h

Index: public/web/WebActiveWheelFlingParameters.h
diff --git a/public/web/WebActiveWheelFlingParameters.h b/public/web/WebActiveWheelFlingParameters.h
index 82a09a38a4048cdf7f5c31366fee9d53fbb172ef..a23f5d5b9ba627cf2b3fb3ec54e28423fb66083d 100644
--- a/public/web/WebActiveWheelFlingParameters.h
+++ b/public/web/WebActiveWheelFlingParameters.h
@@ -28,6 +28,7 @@
 
 #include "../platform/WebCommon.h"
 #include "../platform/WebFloatPoint.h"
+#include "../platform/WebGestureDevice.h"
 #include "../platform/WebPoint.h"
 #include "../platform/WebSize.h"
 #include "WebInputEvent.h"
@@ -39,13 +40,15 @@ struct WebActiveWheelFlingParameters {
     WebPoint point;
     WebPoint globalPoint;
     int modifiers;
-    WebGestureEvent::SourceDevice sourceDevice;
+    // TODO(rjkroege): Restore typing once chromium side lands
+    // (http://crbug.com/343327)
+    int sourceDevice;
     WebSize cumulativeScroll;
     double startTime;
 
     WebActiveWheelFlingParameters()
         : modifiers(0)
-        , sourceDevice(WebGestureEvent::Touchpad)
+        , sourceDevice(WebGestureDeviceTouchpad)
         , startTime(0)
     {
     }