Move SkPaint mangement for 2D canvas into CanvasRenderingContext2DState

Source/platform/graphics/DrawLooperBuilder.cpp

 /*
  * Copyright (C) 2013 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 45 matching lines @@
 {
     return adoptRef(m_skDrawLooperBuilder.detachLooper());
 }
 
 void DrawLooperBuilder::addUnmodifiedContent()
 {
     SkLayerDrawLooper::LayerInfo info;
     m_skDrawLooperBuilder.addLayerOnTop(info);
 }
 
-// This replicates the old skia behavior when it used to take radius for blur. Now it takes sigma.
-static SkScalar RadiusToSigma(SkScalar radius)
-{
-    SkASSERT(radius > 0);
-    return 0.57735f * radius + 0.5f;
-}
-
 void DrawLooperBuilder::addShadow(const FloatSize& offset, float blur, const Color& color,
     ShadowTransformMode shadowTransformMode, ShadowAlphaMode shadowAlphaMode)
 {
     // Detect when there's no effective shadow.
     if (!color.alpha())
         return;
 
     SkColor skColor = color.rgb();
 
     SkLayerDrawLooper::LayerInfo info;
@@ skipping 11 matching lines @@
 
     if (blur)
         info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit; // our blur
     info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
     info.fOffset.set(offset.width(), offset.height());
     info.fPostTranslate = (shadowTransformMode == ShadowIgnoresTransforms);
 
     SkPaint* paint = m_skDrawLooperBuilder.addLayerOnTop(info);
 
     if (blur) {
-        const SkScalar sigma = RadiusToSigma(blur / 2);
+        const SkScalar sigma = skBlurRadiusToSigma(blur);
         uint32_t mfFlags = SkBlurMaskFilter::kHighQuality_BlurFlag;
         if (shadowTransformMode == ShadowIgnoresTransforms)
             mfFlags |= SkBlurMaskFilter::kIgnoreTransform_BlurFlag;
         RefPtr<SkMaskFilter> mf = adoptRef(SkBlurMaskFilter::Create(kNormal_SkBlurStyle, sigma, mfFlags));
         paint->setMaskFilter(mf.get());
     }
 
     RefPtr<SkColorFilter> cf = adoptRef(SkColorFilter::CreateModeFilter(skColor, SkXfermode::kSrcIn_Mode));
     paint->setColorFilter(cf.get());
 }
 
 } // namespace blink