Make SVG painting independent of GraphicsContext's alpha state

Source/platform/graphics/skia/SkiaUtils.cpp

 /*
  * Copyright (c) 2006,2007,2008, 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 342 matching lines @@
     // discouraged. Always drawing with AA can negatively impact performance
     // though - that's why it's not always on.
     SkScalar widthExpansion, heightExpansion;
     if (totalMatrix.getType() & SkMatrix::kAffine_Mask)
         widthExpansion = totalMatrix[SkMatrix::kMSkewY], heightExpansion = totalMatrix[SkMatrix::kMSkewX];
     else
         widthExpansion = totalMatrix[SkMatrix::kMScaleX], heightExpansion = totalMatrix[SkMatrix::kMScaleY];
     return destRect.width() * fabs(widthExpansion) < 1 || destRect.height() * fabs(heightExpansion) < 1;
 }
 
+int clampedAlphaForBlending(float alpha)
+{
+    if (alpha < 0)
+        return 0;
+    int roundedAlpha = roundf(alpha * 256);
+    if (roundedAlpha > 256)
+        roundedAlpha = 256;
+    return roundedAlpha;
+}
+
+SkColor multiplyAlpha(SkColor color, float alpha)
+{
+    return multiplyAlpha(color, clampedAlphaForBlending(alpha));
+}
+
+SkColor multiplyAlpha(SkColor color, int alpha)
+{
+    int a = (SkColorGetA(color) * alpha) >> 8;
+    return (color & 0x00FFFFFF) | (a << 24);
+}
+
 }  // namespace blink