Fix RGBA alpha parsing and serialization to adhere to W3 standard.

third_party/WebKit/Source/platform/graphics/Color.cpp

Index: third_party/WebKit/Source/platform/graphics/Color.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/Color.cpp b/third_party/WebKit/Source/platform/graphics/Color.cpp
index 3ad2e4d84d59cb85ee67ae9928e4615f93b9b2ee..3b406bf1a1addf7976e8fa71e0d6b7eb4ab519bc 100644
--- a/third_party/WebKit/Source/platform/graphics/Color.cpp
+++ b/third_party/WebKit/Source/platform/graphics/Color.cpp
@@ -210,7 +210,16 @@ String Color::serializedAsCSSComponentValue() const {
   result.appendNumber(static_cast<unsigned char>(blue()));
   if (colorHasAlpha) {
     result.append(", ");
-    result.appendNumber(alpha() / 255.0f, 6);
+    // See <alphavalue> section in
+    // http://dev.w3.org/csswg/cssom/#serializing-css-values
+    int alphavalue = alpha();
+    float rounded = round(alphavalue * 100 / 255.0f) / 100;
+    if (round(rounded * 255) == alphavalue) {
+      result.appendNumber(rounded, 2);
+    } else {
+      rounded = round(alphavalue * 1000 / 255.0f) / 1000;
+      result.appendNumber(rounded, 3);
+    }
   }
 
   result.append(')');