Make SVG painting independent of GraphicsContext's alpha state

Source/platform/graphics/skia/SkiaUtils.h

Index: Source/platform/graphics/skia/SkiaUtils.h
diff --git a/Source/platform/graphics/skia/SkiaUtils.h b/Source/platform/graphics/skia/SkiaUtils.h
index d3c9b8539856ff875b7307b4723c4299fa20a0f8..a54d28fac2abfdce619ed655b6e1372a0714e65e 100644
--- a/Source/platform/graphics/skia/SkiaUtils.h
+++ b/Source/platform/graphics/skia/SkiaUtils.h
@@ -52,6 +52,17 @@ SkXfermode::Mode PLATFORM_EXPORT WebCoreCompositeToSkiaComposite(CompositeOperat
 CompositeOperator PLATFORM_EXPORT compositeOperatorFromSkia(SkXfermode::Mode);
 WebBlendMode PLATFORM_EXPORT blendModeFromSkia(SkXfermode::Mode);
 
+// Map alpha values from [0, 1] to [0, 256] for alpha blending.
+int PLATFORM_EXPORT clampedAlphaForBlending(float);
+
+// Multiply a color's alpha channel by an additional alpha factor where
+// alpha is in the range [0, 1].
+SkColor PLATFORM_EXPORT multiplyAlpha(SkColor, float);
+
+// Multiply a color's alpha channel by an additional alpha factor where
+// alpha is in the range [0, 256].
+SkColor PLATFORM_EXPORT multiplyAlpha(SkColor, int);
+
 inline SkPaint::FilterLevel WebCoreInterpolationQualityToSkFilterLevel(InterpolationQuality quality)
 {
     // FIXME: this reflects existing client mappings, but should probably