Partial implementation of CSSVariablesMap for CSS Variables CSSOM

Source/core/css/CSSComputedStyleDeclaration.h

Index: Source/core/css/CSSComputedStyleDeclaration.h
diff --git a/Source/core/css/CSSComputedStyleDeclaration.h b/Source/core/css/CSSComputedStyleDeclaration.h
index e628cd8f304f84047f7cade85c86ba8626fbeb68..4f8173fabed9760d40afe0b3765803af253e5d1c 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.h
+++ b/Source/core/css/CSSComputedStyleDeclaration.h
@@ -22,9 +22,13 @@
 #define CSSComputedStyleDeclaration_h
 
 #include "core/css/CSSStyleDeclaration.h"
+#include "core/css/CSSVariablesMap.h"
 #include "core/rendering/style/RenderStyleConstants.h"
-#include <wtf/RefPtr.h>
-#include <wtf/text/WTFString.h>
+#include "wtf/HashMap.h"
+#include "wtf/RefPtr.h"
+#include "wtf/text/AtomicString.h"
+#include "wtf/text/AtomicStringHash.h"
+#include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
@@ -99,6 +103,14 @@ private:
     virtual String getPropertyValueInternal(CSSPropertyID);
     virtual void setPropertyInternal(CSSPropertyID, const String& value, bool important, ExceptionCode&);
 
+    virtual PassRefPtr<CSSVariablesMap> var() OVERRIDE { return CSSVariablesMap::create(this); }

[esprehn, 2013/07/10 02:42:11]

This isn't correct, you need to keep it in a member variable. For example I can
do: s = getComputedStyle(...); s.var.expando = 1; assert (s.var.expando  == 1);
but since you return a brand new one every time expando will disappear.

[alancutter (OOO until 2018), 2013/07/10 11:18:13]

CSSStyleDeclaration now has a RefPtr to CSSVariablesMap. The map now has a raw
pointer to CSSStyleDeclaration that gets nullified on style's destruction.

It's still possible to lose access to the same CSSVariablesMap JavaScript object
via the el.style.var pathway should the style declaration get deallocated during
the page's lifetime. This is perhaps an issue with style in general as any
expando declared on the style object would also be lost.

I had attempted a static mapping from CSSStyleDeclaration to CSSVariablesMap to
avoid adding extra weight onto the style declaration classes but this approach
is not as robust as the one you had suggested in IRC which is what I've
implemented here.

+    const HashMap<AtomicString, String>* variableMap() const;
+    virtual unsigned variableCount() const OVERRIDE;
+    virtual String variableValue(const AtomicString& name) const OVERRIDE;
+    virtual void setVariableValue(const AtomicString& name, const String& value, ExceptionCode&) OVERRIDE;
+    virtual bool removeVariable(const AtomicString& name) OVERRIDE;
+    virtual void clearVariables(ExceptionCode&) OVERRIDE;
+
     virtual bool cssPropertyMatches(CSSPropertyID, const CSSValue*) const OVERRIDE;
 
     PassRefPtr<CSSValue> valueForShadow(const ShadowData*, CSSPropertyID, const RenderStyle*) const;