Canvas2d: Implement rerouting event by hit region's control.

third_party/WebKit/Source/modules/canvas2d/EventHitRegion.cpp

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "modules/canvas2d/EventHitRegion.h"
-
-#include "core/dom/Document.h"
-#include "core/html/HTMLCanvasElement.h"
-#include "core/layout/LayoutBox.h"
-#include "core/page/Page.h"
-#include "modules/canvas2d/CanvasRenderingContext2D.h"
-#include "modules/canvas2d/HitRegion.h"
-
-namespace blink {
-
-String EventHitRegion::regionIdFromAbsoluteLocation(HTMLCanvasElement& canvas, const LayoutPoint& location)
-{
-    CanvasRenderingContext* context = canvas.renderingContext();
-    if (!context || !context->is2d())
-        return String();
-
-    Document& document = canvas.document();
-    document.updateLayoutTreeForNode(&canvas);
-
-    // Adjust offsetLocation to be relative to the canvas's position.
-    LayoutBox* box = canvas.layoutBox();
-    FloatPoint localPos = box->absoluteToLocal(FloatPoint(location), UseTransforms);
-    if (box->hasBorderOrPadding())
-        localPos.move(-box->contentBoxOffset());
-    localPos.scale(canvas.width() / box->contentWidth(), canvas.height() / box->contentHeight());
-
-    HitRegion* hitRegion = toCanvasRenderingContext2D(context)->hitRegionAtPoint(localPos);
-    if (!hitRegion || hitRegion->id().isEmpty())
-        return String();
-
-    return hitRegion->id();
-}
-
-} // namespace blink