Remove redundant Mac event structures

Source/platform/mac/ScrollElasticityController.mm

Index: Source/platform/mac/ScrollElasticityController.mm
diff --git a/Source/platform/mac/ScrollElasticityController.mm b/Source/platform/mac/ScrollElasticityController.mm
index 09e239be00279396468764023ad0d1a8c44f13e8..e01dcabb17a9f9f3b689d8658d1f79245d1ca838 100644
--- a/Source/platform/mac/ScrollElasticityController.mm
+++ b/Source/platform/mac/ScrollElasticityController.mm
@@ -160,8 +160,10 @@ bool ScrollElasticityController::handleWheelEvent(const PlatformWheelEvent& whee
     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();
@@ -170,20 +172,6 @@ bool ScrollElasticityController::handleWheelEvent(const PlatformWheelEvent& whee
     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;