Implement image-rendering:pixelated for accelerated 2D canvases.

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 68 matching lines @@
     : HTMLElement(canvasTag, document)
     , DocumentVisibilityObserver(document)
     , m_size(DefaultWidth, DefaultHeight)
     , m_ignoreReset(false)
     , m_accelerationDisabled(false)
     , m_externallyAllocatedMemory(0)
     , m_originClean(true)
     , m_didFailToCreateImageBuffer(false)
     , m_didClearImageBuffer(false)
 {
+    setHasCustomStyleCallbacks();
 }
 
 DEFINE_NODE_FACTORY(HTMLCanvasElement)
 
 HTMLCanvasElement::~HTMLCanvasElement()
 {
     resetDirtyRect();
     v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(-m_externallyAllocatedMemory);
 #if !ENABLE(OILPAN)
     HashSet<RawPtr<CanvasObserver> >::iterator end = m_observers.end();
@@ skipping 13 matching lines @@
 }
 
 RenderObject* HTMLCanvasElement::createRenderer(RenderStyle* style)
 {
     LocalFrame* frame = document().frame();
     if (frame && frame->script().canExecuteScripts(NotAboutToExecuteScript))
         return new RenderHTMLCanvas(this);
     return HTMLElement::createRenderer(style);
 }
 
+void HTMLCanvasElement::didRecalcStyle(StyleRecalcChange)
+{
+    m_imageBuffer->setFilterLevel(computedStyle()->imageRendering() == ImageRenderingPixelated ? SkPaint::kNone_FilterLevel : SkPaint::kLow_FilterLevel);

[Justin Novosad, 2014/09/11 15:42:30]

You need to verify hasImageBuffer() here.  If the canvas has not yet been drawn
to, m_imageBuffer may still be uninitialized.
I would like to see a layout test where you draw to the canvas, then re-size the
canvas (which will delete the image buffer), the re-draw to the canvas, which
triggers an immediate style recalc in
HTMLCanvasElement::createImageBufferSurface (because it calls computedStyle).
That test needs to not crash and it needs to respect the pixelated rendering
setting.

+}
+
 Node::InsertionNotificationRequest HTMLCanvasElement::insertedInto(ContainerNode* node)
 {
     setIsInCanvasSubtree(true);
     return HTMLElement::insertedInto(node);
 }
 
 void HTMLCanvasElement::addObserver(CanvasObserver* observer)
 {
     m_observers.add(observer);
 }
@@ skipping 351 matching lines @@
     if (RuntimeEnabledFeatures::displayList2dCanvasEnabled()) {
         OwnPtr<ImageBufferSurface> surface = adoptPtr(new RecordingImageBufferSurface(size(), opacityMode));
         if (surface->isValid())
             return surface.release();
     }
 
     if (shouldAccelerate(deviceSize)) {
         if (document().settings())
             *msaaSampleCount = document().settings()->accelerated2dCanvasMSAASampleCount();
         OwnPtr<ImageBufferSurface> surface = adoptPtr(new Canvas2DImageBufferSurface(size(), opacityMode, *msaaSampleCount));
+        surface->setFilterLevel(computedStyle()->imageRendering() == ImageRenderingPixelated ? SkPaint::kNone_FilterLevel : SkPaint::kLow_FilterLevel);
         if (surface->isValid())
             return surface.release();
     }
 
     return adoptPtr(new UnacceleratedImageBufferSurface(size(), opacityMode));
 }
 
 void HTMLCanvasElement::createImageBuffer()
 {
     createImageBufferInternal();
@@ skipping 237 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }