Add image-rendering: pixelated.

Source/core/rendering/RenderHTMLCanvas.cpp

Index: Source/core/rendering/RenderHTMLCanvas.cpp
diff --git a/Source/core/rendering/RenderHTMLCanvas.cpp b/Source/core/rendering/RenderHTMLCanvas.cpp
index 41a294209064a7e9999a021ad08e49db18a7d5c8..1aa23b1323f013123e407ad7c3ee5f95934c1d7c 100644
--- a/Source/core/rendering/RenderHTMLCanvas.cpp
+++ b/Source/core/rendering/RenderHTMLCanvas.cpp
@@ -67,7 +67,18 @@ void RenderHTMLCanvas::paintReplaced(PaintInfo& paintInfo, const LayoutPoint& pa
 
     // FIXME: InterpolationNone should be used if ImageRenderingOptimizeContrast is set.
     // See bug for more details: crbug.com/353716.
-    InterpolationQuality interpolationQuality = style()->imageRendering() == ImageRenderingOptimizeContrast ? InterpolationLow : CanvasDefaultInterpolationQuality;
+    InterpolationQuality interpolationQuality;
+    switch (style()->imageRendering()) {
+    case ImageRenderingOptimizeContrast:
+        interpolationQuality = InterpolationLow;

[Mike Lawther (Google), 2014/06/20 04:26:50]

These should really be the same, ie InterpolationNone. From memory, it was only
set to InterpolationLow because that was the value that CoreGraphics used to
mean 'nearest neighbour'

[jackhou, 2014/06/20 07:14:44]

Done.

[jackhou, 2014/06/20 08:35:42]

I realized this would require updating all the tests, which differ by platform.
Also, it would be shipped immediately, whereas pixelated is still experimental.
So probably best to leave it unchanged for now and address it in the follow-up
CL.

+        break;
+    case ImageRenderingPixelated:
+        interpolationQuality = InterpolationNone;

[Mike Lawther (Google), 2014/06/20 04:26:50]

Strictly according to spec, we only use nearest neighbour if we are scaling up.
If we are scaling down, then we should be using the default scaling (quoth the
spec: "When scaling the image up, the "nearest neighbor" or similar algorithm
must be used, so that the image appears to be simply composed of very large
pixels. When scaling down, this is the same as auto.").

I'm fine with filing a bug about this with a FIXME.

[jackhou, 2014/06/20 07:14:44]

Done.

+        break;
+    default:
+        interpolationQuality = CanvasDefaultInterpolationQuality;
+    }
+
     InterpolationQuality previousInterpolationQuality = context->imageInterpolationQuality();
     context->setImageInterpolationQuality(interpolationQuality);
     toHTMLCanvasElement(node())->paint(context, paintRect);