OverscrollGlow for mainThread-{BLINK CHANGES}

Source/core/page/EventHandler.h

Index: Source/core/page/EventHandler.h
diff --git a/Source/core/page/EventHandler.h b/Source/core/page/EventHandler.h
index a2314445140e2e5224e4b092500258fd976636db..84c4dc4d09ac51dd1eaddcf1515c333b0a6579d6 100644
--- a/Source/core/page/EventHandler.h
+++ b/Source/core/page/EventHandler.h
@@ -128,6 +128,9 @@ public:
 
     void resizeScrollableAreaDestroyed();
 
+    FloatSize unusedDeltaForTesting() const { return m_unusedDelta; }
+    FloatSize accumulatedRootOverscrollForTesting() const { return m_accumulatedRootOverscroll; }
+

[majidvp, 2015/06/03 17:36:41]

This is minor but I am not a big fan of exposing these "Testing" functions. I
feel a better testing approach would be to
use a mock of WebViewClient similar to how other tests are implemented.

Which is  This is not a major issue and can perhaps be addressed in a follow-up
patch. bokan@ wdyt?

[bokan, 2015/06/03 19:12:19]

Agreed, this is an anti-pattern.

[MuVen, 2015/06/04 11:19:59]

Done. But when using mock WebViewClient, we cant check the reset logic
of the unusedDelta and accumulatedRootOverscroll. As Overscroll is not reported
when unusedDelta/accumulatedRootOverscroll is reset. Please let me know your
inputs on this.

[bokan, 2015/06/04 12:05:42]

The reset logic is an internal detail of EventSender so we shouldn't test it
directly. You should be testing the visible output. Another way of putting it:
if the reset logic is broken, what about the output is wrong? Find that and
setup the test so you check it.

In this case, it seems you should have someting like this: one gesture scroll
generate some overscroll, produce another scroll in the opposite direction that
should clear the accumulated delta, then try to overscroll again and confirm the
overscroll amount is what you'd expect if the middle scroll cleared the delta. 

[MuVen, 2015/06/04 14:01:19]

Done. 

     IntPoint lastKnownMousePosition() const;
 
     // Attempts to scroll the DOM tree. If that fails, scrolls the view.
@@ -261,7 +264,9 @@ private:
     //            On output, if provided and a node was scrolled stopNode will point to that node.
     // delta - The delta to scroll by, in the units of the granularity parameter. (e.g. pixels, lines, pages, etc.)
     // absolutePoint - For wheel scrolls - the location, in absolute coordinates, where the event occured.
-    bool scroll(ScrollDirection, ScrollGranularity, Node* startNode = nullptr, Node** stopNode = nullptr, float delta = 1.0f, IntPoint absolutePoint = IntPoint());
+    ScrollResultOneDimensional scroll(ScrollDirection, ScrollGranularity, Node* startNode = nullptr, Node** stopNode = nullptr, float delta = 1.0f, IntPoint absolutePoint = IntPoint());
+
+    void resetOverscroll(bool didScrollX, bool didScrollY);
 
     void customizedScroll(const Node& startNode, ScrollState&);
 
@@ -378,6 +383,9 @@ private:
 
     LayoutSize m_offsetFromResizeCorner; // In the coords of m_resizeScrollableArea.
 
+    FloatSize m_unusedDelta;

[majidvp, 2015/06/03 17:36:41]

If we get rid of the *Testing functions we can remove this data member as well.

[MuVen, 2015/06/04 11:19:58]

Done.

+    FloatSize m_accumulatedRootOverscroll;
+
     bool m_mousePositionIsUnknown;
     // The last mouse movement position this frame has seen in root frame coordinates.
     IntPoint m_lastKnownMousePosition;