Canvas2d: Fix a bug to update incorrect rect bounds for accessibility.

Source/modules/canvas2d/CanvasRenderingContext2D.cpp

Index: Source/modules/canvas2d/CanvasRenderingContext2D.cpp
diff --git a/Source/modules/canvas2d/CanvasRenderingContext2D.cpp b/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
index 924d592daa574b886098c9efb48c5c63637b207b..a147542df3885b9cbce27e41c45d9496229f6952 100644
--- a/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
+++ b/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
@@ -2108,6 +2108,7 @@ void CanvasRenderingContext2D::drawFocusRing(const Path& path)
 
 void CanvasRenderingContext2D::updateElementAccessibility(const Path& path, Element* element)
 {
+    element->document().updateLayoutTreeIfNeeded();

[Justin Novosad, 2015/07/23 19:33:15]

I recently found out that it is much preferable to call
updateLayoutTreeForNodeIfNeeded(elementYouAreInterestedIn) This way, you avoid
triggering a layout and style computation in cases where the computed style of
the canvas is known to be up to date (though other parts of the document may not
be).

[zino, 2015/07/27 13:59:45]

Thank you for information.

BTW, I removed this line in a new patch set.
I'm not sure but we don't need it (to resolve this issue).

     AXObjectCache* axObjectCache = element->document().existingAXObjectCache();
     LayoutBoxModelObject* lbmo = canvas()->layoutBoxModelObject();
     LayoutObject* renderer = canvas()->layoutObject();
@@ -2119,6 +2120,7 @@ void CanvasRenderingContext2D::updateElementAccessibility(const Path& path, Elem
     transformedPath.transform(state().transform());
 
     // Offset by the canvas rect, taking border and padding into account.
+    element->document().updateLayoutIgnorePendingStylesheets();

[Justin Novosad, 2015/07/23 19:33:15]

We should not add new call to this function, unless you have a really good
reason. See the comments in this function in Document.cpp.  Also why is this
necessary? I don't anything that would invalidate layout or style between the
above update and here.

[zino, 2015/07/27 13:59:45]

Please see the http://crbug.com/513763.

We will have to update the |absolute bounding rect| of canvas path.
If there isn't the line, we can't get the correct location(canvas location) from
|renderer->absoluteBoundingBoxRect()|.

     IntRect canvasRect = renderer->absoluteBoundingBoxRect();
     canvasRect.move(lbmo->borderLeft() + lbmo->paddingLeft(), lbmo->borderTop() + lbmo->paddingTop());
     LayoutRect elementRect = enclosingLayoutRect(transformedPath.boundingRect());