The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/282ff5518bc121cfe77a29ddd2b9a465b74daf37

commit 282ff5518bc121cfe77a29ddd2b9a465b74daf37
Author: jinho.bang <jinho.bang@samsung.com>
Date: Mon Apr 18 15:52:01 2016

Canvas2d: fix event.region being null on mouseleave/out events

In the current implementation of canvas hit region, the event.region always has
null in case of mouseleave/mouseout. Because the mouse cursor is already off
boundary of hit region when mouseleave/mouseout event happens.
To solve this problem, keeps the region in mouseenter/mouseover event and then
takes the value in mouseout/mouseleave event.

BUG= 592992 

Review URL: https://codereview.chromium.org/1815093002

Cr-Commit-Position: refs/heads/master@{#387915}

[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/LayoutTests/fast/canvas/canvas-hit-regions-event-test.html
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/core/input/PointerEventManager.cpp
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2D.h
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/modules/canvas2d/HitRegion.cpp
[modify] https://crrev.com/282ff5518bc121cfe77a29ddd2b9a465b74daf37/third_party/WebKit/Source/modules/canvas2d/HitRegion.h

The HitRegion feature was abandoned.