A thread safe CSS calc parser for sizes

Source/core/css/MediaValues.h

Index: Source/core/css/MediaValues.h
diff --git a/Source/core/css/MediaValues.h b/Source/core/css/MediaValues.h
index c163bb682bd524dcf5ae07770b6c61bebc5bfd16..a4f8d737e8312daefd84df64059499225c9f27e5 100644
--- a/Source/core/css/MediaValues.h
+++ b/Source/core/css/MediaValues.h
@@ -35,8 +35,19 @@ public:
     static PassRefPtr<MediaValues> createDynamicIfFrameExists(LocalFrame*);
     virtual PassRefPtr<MediaValues> copy() const = 0;
     virtual bool isSafeToSendToAnotherThread() const = 0;
-    static bool computeLength(double value, CSSPrimitiveValue::UnitTypes, unsigned defaultFontSize, unsigned viewportWidth, unsigned viewportHeight, int& result);
+
+    static bool computeLengthImpl(double value, CSSPrimitiveValue::UnitTypes, unsigned defaultFontSize, unsigned viewportWidth, unsigned viewportHeight, double& result);
+    template<typename T>
+    static bool computeLength(double value, CSSPrimitiveValue::UnitTypes type, unsigned defaultFontSize, unsigned viewportWidth, unsigned viewportHeight, T& result)
+    {
+        double tempResult;
+        if (!computeLengthImpl(value, type, defaultFontSize, viewportWidth, viewportHeight, tempResult))
+            return false;
+        result = roundForImpreciseConversion<T>(tempResult);
+        return true;
+    }
     virtual bool computeLength(double value, CSSPrimitiveValue::UnitTypes, int& result) const = 0;
+    virtual bool computeLength(double value, CSSPrimitiveValue::UnitTypes, double& result) const = 0;
 
     virtual int viewportWidth() const = 0;
     virtual int viewportHeight() const = 0;