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

third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h

Index: third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h
diff --git a/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h b/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h
index 12886881a11c99fdd9d3fa925539f4e45979b6ec..c07c28d2edc646ecab513fe7818ad1d7b52ff7d9 100644
--- a/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h
+++ b/third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.h
@@ -109,6 +109,7 @@ public:
     virtual unsigned hitRegionsCount() const { return 0; }
     virtual void setFont(const String&) { }
     virtual void styleDidChange(const ComputedStyle* oldStyle, const ComputedStyle& newStyle) { }
+    virtual std::pair<Element*, String> getControlAndIDIfHitRegionExists(const LayoutPoint& location) { return std::make_pair(nullptr, String()); }

[Justin Novosad, 2016/02/05 15:22:53]

I think this default implementation (and the all the other ones that should
never be invoked on a WebGL canvas) should have ASSERT_NOT_REACHED();  As was
done in the WebGL section below.

[zino, 2016/02/12 15:26:19]

Done.

 
     // WebGL-specific interface
     virtual bool is3d() const { return false; }