Fix float parsing in srcset

Source/core/html/parser/HTMLSrcsetParser.cpp

 /*
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  * 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.
@@ skipping 79 matching lines @@
     template<typename CharType>
     float toFloat(const CharType* attribute, bool& isValid)
     {
         // Make sure the is a valid floating point number
         // https://html.spec.whatwg.org/multipage/infrastructure.html#valid-floating-point-number
         unsigned lengthExcludingDescriptor = length - 1;
         if (lengthExcludingDescriptor > 0 && *(attribute + start) == '+') {
             isValid = false;
             return 0;
         }
-        return charactersToFloat(attribute + start, lengthExcludingDescriptor, &isValid);
+        Decimal result = parseToDecimalForNumberType(String(attribute + start, lengthExcludingDescriptor));
+        isValid = result.isFinite();
+        if (!isValid)
+            return 0;
+        return clampTo<float>(result.toDouble());

[tkent, 2015/08/25 10:02:46]

This looks to have a behavior change for numbers greater than the float limit.
Do we have a test?

[Yoav Weiss, 2015/08/25 10:07:58]

I didn't mean for that to be a behavior change. Is there a difference between
casting a double to a float (which was the previous behavior) and clampTo?
Should this be a static_case instead?

[tkent, 2015/08/25 10:14:23]

AFAIK, static_cast<float>(greater-than-float-max) returns Infinity, and
clampTo<float>() returns the maximum value of float.

     }
 };
 
 template<typename CharType>
 static void appendDescriptorAndReset(const CharType* attributeStart, const CharType*& descriptorStart, const CharType* position, Vector<DescriptorToken>& descriptors)
 {
     if (position > descriptorStart)
         descriptors.append(DescriptorToken(descriptorStart - attributeStart, position - descriptorStart));
     descriptorStart = 0;
 }
@@ skipping 320 matching lines @@
     Vector<ImageCandidate> imageCandidates;
     imageCandidates.append(srcsetImageCandidate);
 
     if (!srcAttribute.isEmpty())
         imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), DescriptorParsingResult(), ImageCandidate::SrcOrigin));
 
     return pickBestImageCandidate(deviceScaleFactor, sourceSize, imageCandidates).toString();
 }
 
 }