Improve default value handling for SVGSVGElement.width/height

third_party/WebKit/Source/core/svg/SVGAnimatedLength.h

 /*
  * Copyright (C) 2014 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 22 matching lines @@
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/svg/SVGLengthTearOff.h"
 #include "core/svg/properties/SVGAnimatedProperty.h"
 
 namespace blink {
 
 class SVGAnimatedLength : public SVGAnimatedProperty<SVGLength>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
-    static SVGAnimatedLength* create(SVGElement* contextElement, const QualifiedName& attributeName, SVGLength* initialValue)
+    static SVGAnimatedLength* create(SVGElement* contextElement, const QualifiedName& attributeName, SVGLength* initialValue, const char* defaultValue = nullptr)
     {
-        return new SVGAnimatedLength(contextElement, attributeName, initialValue);
+        return new SVGAnimatedLength(contextElement, attributeName, initialValue, defaultValue);
     }
 
+    void setDefaultValue();
     void setDefaultValueAsString(const String&);
     SVGParsingError setBaseValueAsString(const String&) override;
 
 protected:
-    SVGAnimatedLength(SVGElement* contextElement, const QualifiedName& attributeName, SVGLength* initialValue)
+    SVGAnimatedLength(SVGElement* contextElement, const QualifiedName& attributeName, SVGLength* initialValue, const char* defaultValue = nullptr)
         : SVGAnimatedProperty<SVGLength>(contextElement, attributeName, initialValue)
+        , m_defaultValue(defaultValue)
     {
     }
+
+    const char* m_defaultValue;

[pdr., 2016/04/18 21:25:14]

This seems like a memory regression since it costs one pointer per length. Is
there any other way to solve this, for example by special-casing
svgAttributeChanged?

[pdr., 2016/04/18 21:36:23]

Adding a little more info... I am wondering if we can avoid storing one default
per length, and instead store the default just once.

[fs, 2016/04/18 21:55:07]

We could probably fix it by a crutch in parseAttribute.
There are at least a few different methods (that I've been able to think of)
that avoids increasing the attribute objects. Some better and some worse I'm
sure - my current favorite is a "dictionary" (small index + string table).

 };
 
 } // namespace blink
 
 #endif // SVGAnimatedLength_h