Remove redundant Mac event structures

Source/platform/mac/ScrollElasticityController.mm

 /*
  * Copyright (C) 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 142 matching lines @@
         if (wheelEvent.momentumPhase() == PlatformWheelEventPhaseEnded) {
             m_ignoreMomentumScrolls = false;
             return true;
         }
         return false;
     }
 
     if (!shouldHandleEvent(wheelEvent))
         return false;
 
-    float deltaX = m_overflowScrollDelta.width();
-    float deltaY = m_overflowScrollDelta.height();
+    float deltaX = m_overflowScrollDelta.width() - wheelEvent.deltaX();
+    float deltaY = m_overflowScrollDelta.height() - wheelEvent.deltaY();
+    float eventCoalescedDeltaX = -wheelEvent.deltaX();
+    float eventCoalescedDeltaY = -wheelEvent.deltaY();
 
     // Reset overflow values because we may decide to remove delta at various points and put it into overflow.
     m_overflowScrollDelta = FloatSize();
 
     IntSize stretchAmount = m_client->stretchAmount();
     bool isVerticallyStretched = stretchAmount.height();
     bool isHorizontallyStretched = stretchAmount.width();
 
-    float eventCoalescedDeltaX;
-    float eventCoalescedDeltaY;
-
-    if (isVerticallyStretched || isHorizontallyStretched) {
-        eventCoalescedDeltaX = -wheelEvent.unacceleratedScrollingDeltaX();
-        eventCoalescedDeltaY = -wheelEvent.unacceleratedScrollingDeltaY();
-    } else {
-        eventCoalescedDeltaX = -wheelEvent.deltaX();
-        eventCoalescedDeltaY = -wheelEvent.deltaY();
-    }
-
-    deltaX += eventCoalescedDeltaX;
-    deltaY += eventCoalescedDeltaY;
-
     // Slightly prefer scrolling vertically by applying the = case to deltaY
     if (fabsf(deltaY) >= fabsf(deltaX))
         deltaX = 0;
     else
         deltaY = 0;
 
     bool shouldStretch = false;
 
     PlatformWheelEventPhase momentumPhase = wheelEvent.momentumPhase();
 
@@ skipping 251 matching lines @@
             return false;
     }
 
     // The event is going to either cause scrolling or rubber banding.
     return true;
 }
 
 } // namespace blink
 
 #endif // USE(RUBBER_BANDING)