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

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index 7ce2ab15d2123fd7ffbe0fb1ff33a233e4d4e435..b85e9bb3dbd76999547a6eb06ce86d62d10a9fe6 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -86,6 +86,7 @@ inline HTMLCanvasElement::HTMLCanvasElement(Document& document)
     , m_didFailToCreateImageBuffer(false)
     , m_didClearImageBuffer(false)
 {
+    setHasCustomStyleCallbacks();
 }
 
 DEFINE_NODE_FACTORY(HTMLCanvasElement)
@@ -119,6 +120,11 @@ RenderObject* HTMLCanvasElement::createRenderer(RenderStyle* style)
     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);
@@ -490,6 +496,7 @@ PassOwnPtr<ImageBufferSurface> HTMLCanvasElement::createImageBufferSurface(const
         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();
     }