Refactor srcset parser to align it with spec changes

Source/core/html/parser/HTMLSrcsetParser.h

Index: Source/core/html/parser/HTMLSrcsetParser.h
diff --git a/Source/core/html/parser/HTMLSrcsetParser.h b/Source/core/html/parser/HTMLSrcsetParser.h
index cdf3c1d64ae4f34d372b848315cac30102f48f89..2efeacd952c1c731d5752b56ab0871a9cf4037e4 100644
--- a/Source/core/html/parser/HTMLSrcsetParser.h
+++ b/Source/core/html/parser/HTMLSrcsetParser.h
@@ -36,19 +36,20 @@
 namespace WebCore {
 
 struct DescriptorParsingResult {
-    float scaleFactor;
+    float density;
     int resourceWidth;
+    int resourceHeight;
 
     DescriptorParsingResult()
     {
-        scaleFactor = -1.0;
+        density = -1.0;

[eseidel, 2014/05/28 22:24:59]

Bleh.  Sentinel values/in-band data.  :(

You might want to make these have real accessors that ASSERT that they're not
called when these values are bad...  You may end up with very strange bugs if
someone grabs these and fails to check foundFoo.

[Yoav Weiss, 2014/05/29 05:17:40]

OK, I'll turn that into a class with proper getters.

         resourceWidth = -1;
+        resourceHeight = -1;
     }
 
-    bool foundDescriptor() const
-    {
-        return (scaleFactor >= 0 || resourceWidth >= 0);
-    }
+    bool foundDensity() { return density >= 0; }

[eseidel, 2014/05/28 22:24:59]

I think "hasDensitiy" might be more consistent with other code in blink, but
found can be OK if it matches the callers.  Up to you.

[Yoav Weiss, 2014/05/29 05:17:40]

Sure

+    bool foundWidth() { return resourceWidth >= 0; }

[eseidel, 2014/05/28 22:24:59]

Can these ever be set to negative numbers intentionally?  What should the
behavior be?  Do we need a setter which ignores negative values?  Ah, the
pit-falls of sentinal values.

[Yoav Weiss, 2014/05/29 05:17:40]

No
Yeah, I'll add that

+    bool foundHeight() { return resourceHeight >= 0; }
 };
 
 class ImageCandidate {
@@ -59,13 +60,13 @@ public:
     };
 
     ImageCandidate()
-        : m_scaleFactor(1.0)
+        : m_density(1.0)
     {
     }
 
     ImageCandidate(const String& source, unsigned start, unsigned length, const DescriptorParsingResult& result, OriginAttribute originAttribute)
         : m_string(source.createView(start, length))
-        , m_scaleFactor(result.scaleFactor)
+        , m_density(result.density)
         , m_resourceWidth(result.resourceWidth)
         , m_originAttribute(originAttribute)
     {
@@ -81,14 +82,14 @@ public:
         return AtomicString(m_string.toString());
     }
 
-    void setScaleFactor(float factor)
+    void setDensity(float factor)
     {
-        m_scaleFactor = factor;
+        m_density = factor;
     }
 
-    float scaleFactor() const
+    float density() const
     {
-        return m_scaleFactor;
+        return m_density;
     }
 
     int resourceWidth() const
@@ -108,7 +109,7 @@ public:
 
 private:
     StringView m_string;
-    float m_scaleFactor;
+    float m_density;
     int m_resourceWidth;
     OriginAttribute m_originAttribute;
 };