Implement CSS luminance masking using skia SkLumaMaskXfermode class.

Source/core/platform/graphics/skia/NativeImageSkia.cpp

 /*
  * Copyright (c) 2008, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 27 matching lines @@
 #include "core/platform/graphics/FloatSize.h"
 #include "core/platform/graphics/GraphicsContext.h"
 #include "core/platform/graphics/Image.h"
 #include "core/platform/graphics/chromium/DeferredImageDecoder.h"
 #include "core/platform/graphics/skia/SkiaUtils.h"
 #include "skia/ext/image_operations.h"
 #include "third_party/skia/include/core/SkMatrix.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkScalar.h"
 #include "third_party/skia/include/core/SkShader.h"
+#include "third_party/skia/include/effects/SkLumaXfermode.h"
 
 #include <limits>
 #include <math.h>
 
 namespace WebCore {
 
 static bool nearlyIntegral(float value)
 {
     return fabs(value - floorf(value)) < std::numeric_limits<float>::epsilon();
 }
@@ skipping 259 matching lines @@
 
 static bool hasNon90rotation(GraphicsContext* context)
 {
     return !context->getTotalMatrix().rectStaysRect();
 }
 
 void NativeImageSkia::draw(GraphicsContext* context, const SkRect& srcRect, const SkRect& destRect, PassRefPtr<SkXfermode> compOp) const
 {
     TRACE_EVENT0("skia", "NativeImageSkia::draw");
     SkPaint paint;
-    paint.setXfermode(compOp.get());
+    if (context->drawLuminanceMask()) {

[eseidel, 2013/09/19 15:10:37]

I believe blink style says {} are avoided when there is only one line in the
clause.

+        paint.setXfermode(SkLumaMaskXfermode::Create(SkXfermode::kSrcOver_Mode));
+    } else {
+        paint.setXfermode(compOp.get());
+    }
     paint.setAlpha(context->getNormalizedAlpha());
     paint.setLooper(context->drawLooper());
     // only antialias if we're rotated or skewed
     paint.setAntiAlias(hasNon90rotation(context));
 
     ResamplingMode resampling;
     if (context->isAccelerated()) {
         resampling = LinearResampling;
     } else if (context->printing()) {
         resampling = NoResampling;
@@ skipping 116 matching lines @@
     // origin of the destination rect, which is what WebKit expects. Skia uses
     // the coordinate system origin as the base for the pattern. If WebKit wants
     // a shifted image, it will shift it from there using the shaderTransform.
     float adjustedX = phase.x() + normSrcRect.x() * scale.width();
     float adjustedY = phase.y() + normSrcRect.y() * scale.height();
     shaderTransform.postTranslate(SkFloatToScalar(adjustedX), SkFloatToScalar(adjustedY));
     shader->setLocalMatrix(shaderTransform);
 
     SkPaint paint;
     paint.setShader(shader.get());
-    paint.setXfermode(WebCoreCompositeToSkiaComposite(compositeOp, blendMode).get());
+    if (context->drawLuminanceMask()) {
+        paint.setXfermode(SkLumaMaskXfermode::Create(SkXfermode::kSrcOver_Mode));
+    } else {
+        paint.setXfermode(WebCoreCompositeToSkiaComposite(compositeOp, blendMode).get());
+    }
 
     paint.setFilterBitmap(resampling == LinearResampling);
     if (useBicubicFilter)
         paint.setFilterLevel(SkPaint::kHigh_FilterLevel);
 
     context->drawRect(destRect, paint);
 }
 
 bool NativeImageSkia::shouldCacheResampling(const SkISize& scaledImageSize, const SkIRect& scaledImageSubset) const
 {
@@ skipping 61 matching lines @@
 SkIRect NativeImageSkia::ImageResourceInfo::rectInSubset(const SkIRect& otherScaledImageSubset)
 {
     if (!scaledImageSubset.contains(otherScaledImageSubset))
         return SkIRect::MakeEmpty();
     SkIRect subsetRect = otherScaledImageSubset;
     subsetRect.offset(-scaledImageSubset.x(), -scaledImageSubset.y());
     return subsetRect;
 }
 
 } // namespace WebCore