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 {
 
+// Report Overscroll if OverscrollDelta is greater than minimumOverscrollDelta
+// to maintain consistency as did in compositor.
+static const float minimumOverscrollDelta = 0.1;

[majidvp, 2015/07/09 18:01:18]

Please move this next to other constants.

[MuVen, 2015/07/09 18:10:06]

Done.

+
+static inline FloatSize adjustOverscoll(FloatSize unusedDelta)

[majidvp, 2015/07/09 18:01:18]

Given that there is a single member func that uses this I think it help with
readability if you move this just above where it is being used.

In any case it should not be before using statements or constant definitions.

[MuVen, 2015/07/09 18:10:06]

Done.

+{
+    if (std::abs(unusedDelta.width()) < minimumOverscrollDelta)
+        unusedDelta.setWidth(0);
+    if (std::abs(unusedDelta.height()) < minimumOverscrollDelta)
+        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 2127 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 = adjustOverscoll(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);
@@ skipping 1666 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink