Plumb gesture source value through Blink.

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1856 matching lines @@
 
     // Create synthetic wheel events as necessary for fling.
     if (m_gestureAnimation) {
         if (m_gestureAnimation->animate(frameTime.lastFrameTimeMonotonic))
             scheduleAnimation();
         else {
             endActiveFlingAnimation();
 
             PlatformGestureEvent endScrollEvent(PlatformEvent::GestureScrollEnd,
                 m_positionOnFlingStart, m_globalPositionOnFlingStart,
-                IntSize(), 0, PlatformEvent::NoModifiers);
+                IntSize(), 0, PlatformEvent::NoModifiers, PlatformGestureSourceUninitialized);

[tdresser, 2015/10/14 15:14:20]

Uninitialized doesn't feel quite right here. It might be better to keep track of
what device caused the fling.

[wjmaclean, 2015/10/14 15:55:09]

Done.

Turns out WebViewImpl already had a var for this, though I had to convert it
from bool :-/

             endScrollEvent.setScrollGestureData(0, 0, 0, 0, true, false, -1 /* null plugin id */);
 
             mainFrameImpl()->frame()->eventHandler().handleGestureScrollEnd(endScrollEvent);
         }
     }
 
     if (!m_page)
         return;
 
     PageWidgetDelegate::animate(*m_page, frameTime.lastFrameTimeMonotonic);
@@ skipping 2562 matching lines @@
     if (m_pageColorOverlay)
         m_pageColorOverlay->update();
     if (InspectorOverlay* overlay = inspectorOverlay()) {
         PageOverlay* inspectorPageOverlay = overlay->pageOverlay();
         if (inspectorPageOverlay)
             inspectorPageOverlay->update();
     }
 }
 
 } // namespace blink