Reset unusedDelta on Onverscroll for residual values.

Source/core/input/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * 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.
@@ skipping 79 matching lines @@
 #include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollAnimator.h"
 #include "platform/scroll/Scrollbar.h"
 #include "wtf/Assertions.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/TemporaryChange.h"
 
 namespace blink {
 
+const float kEpsilon = 0.1;

[majidvp, 2015/07/09 15:02:46]

Please add a comment explaining why 0.1. I suppose it is to be consistent with
CC.

Also make it static and choose a more descriptive name e.g.,
minimumOverscrollDelta and move it next to other constants.

[MuVen, 2015/07/09 17:51:34]

Done.

+
+bool IsApproxZero(float value)

[majidvp, 2015/07/09 15:02:46]

This function is superfluous as it is only used once.
Please get rid of it and inline the calculation.

[MuVen, 2015/07/09 17:51:35]

Done.

+{
+    return std::abs(value) < kEpsilon;
+}
+
+FloatSize ZeroSmallComponents(FloatSize unUsedDelta)

[majidvp, 2015/07/09 15:02:46]

I think the name should reflect that it is meant to be used for overscroll and
not as a generic utility. I prefer using the same naming as CC for consistency
which is |adjustOverscoll|.

Also, I think a utility function like this should be made static inline.

[MuVen, 2015/07/09 17:51:35]

Done.

+{
+    if (IsApproxZero(unUsedDelta.width()))

[majidvp, 2015/07/09 15:02:46]

s/unUsedDelta/unusedDelta/ for consistency

[MuVen, 2015/07/09 17:51:35]

Done.

+        unUsedDelta.setWidth(0);
+    if (IsApproxZero(unUsedDelta.height()))
+        unUsedDelta.setHeight(0);
+    return unUsedDelta;
+}
+
 using namespace HTMLNames;
 
 // The link drag hysteresis is much larger than the others because there
 // needs to be enough space to cancel the link press without starting a link drag,
 // and because dragging links is rare.
 static const int LinkDragHysteresis = 40;
 static const int ImageDragHysteresis = 5;
 static const int TextDragHysteresis = 3;
 static const int GeneralDragHysteresis = 3;
 
@@ skipping 2126 matching lines @@
 {
     if (didScrollX)
         m_accumulatedRootOverscroll.setWidth(0);
     if (didScrollY)
         m_accumulatedRootOverscroll.setHeight(0);
 }
 
 void EventHandler::handleOverscroll(const ScrollResult& scrollResult, const FloatPoint& position, const FloatSize& velocity)
 {
     FloatSize unusedDelta(scrollResult.unusedScrollDeltaX, scrollResult.unusedScrollDeltaY);
+    unusedDelta = ZeroSmallComponents(unusedDelta);
     resetOverscroll(scrollResult.didScrollX, scrollResult.didScrollY);
     if (unusedDelta != FloatSize()) {
         m_accumulatedRootOverscroll += unusedDelta;
         m_frame->chromeClient().didOverscroll(unusedDelta, m_accumulatedRootOverscroll, position, velocity);
     }
 }
 
 bool EventHandler::handleGestureScrollUpdate(const PlatformGestureEvent& gestureEvent)
 {
     ASSERT(gestureEvent.type() == PlatformEvent::GestureScrollUpdate);
 
     FloatSize delta(gestureEvent.deltaX(), gestureEvent.deltaY());
+

[majidvp, 2015/07/09 15:02:46]

unnecessary blank line.

[MuVen, 2015/07/09 17:51:35]

Done.

     if (delta.isZero())
         return false;
 
     Node* node = m_scrollGestureHandlingNode.get();
     if (node) {
         LayoutObject* layoutObject = node->layoutObject();
         if (!layoutObject)
             return false;
 
         RefPtrWillBeRawPtr<FrameView> protector(m_frame->view());
@@ skipping 1654 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink