Reset unusedDelta on Onverscroll for residual values.

Source/core/input/EventHandler.cpp

Index: Source/core/input/EventHandler.cpp
diff --git a/Source/core/input/EventHandler.cpp b/Source/core/input/EventHandler.cpp
index ab0864fa0e9ed5b4cbd8e77859449c1b3a9666a7..e109c5b76a8022fc5c85e7bd8f7db3c6f6b1a3cb 100644
--- a/Source/core/input/EventHandler.cpp
+++ b/Source/core/input/EventHandler.cpp
@@ -97,6 +97,22 @@
 
 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
@@ -2243,6 +2259,7 @@ void EventHandler::resetOverscroll(bool didScrollX, bool didScrollY)
 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;
@@ -2255,6 +2272,7 @@ bool EventHandler::handleGestureScrollUpdate(const PlatformGestureEvent& gesture
     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;