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

Source/modules/canvas2d/CanvasRenderingContext2D.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012, 2013 Intel Corporation. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
@@ skipping 2090 matching lines @@
 
     SkIRect dirtyRect;
     if (!computeDirtyRect(path.strokeBoundingRect(strokeData), &dirtyRect))
         return;
 
     didDraw(dirtyRect);
 }
 
 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();
     if (!axObjectCache || !lbmo || !renderer)
         return;
 
     // Get the transformed path.
     Path transformedPath = path;
     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());
     elementRect.moveBy(canvasRect.location());
     axObjectCache->setCanvasObjectBounds(element, elementRect);
 }
 
 void CanvasRenderingContext2D::addHitRegion(const HitRegionOptions& options, ExceptionState& exceptionState)
 {
     if (options.id().isEmpty() && !options.control()) {
@@ skipping 124 matching lines @@
         if (imageType == CanvasRenderingContext2DState::NonOpaqueImage)
             return;
         if (alpha < 0xFF)
             return;
     }
 
     canvas()->buffer()->willOverwriteCanvas();
 }
 
 } // namespace blink