A thread safe CSS calc parser for sizes

Source/core/css/MediaValues.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MediaValues_h
 #define MediaValues_h
 
 #include "core/css/CSSPrimitiveValue.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
@@ skipping 17 matching lines @@
         MousePointer,
         NoPointer,
         UnknownPointer
     };
 
     virtual ~MediaValues() { }
 
     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;
     virtual int deviceWidth() const = 0;
     virtual int deviceHeight() const = 0;
     virtual float devicePixelRatio() const = 0;
     virtual int colorBitsPerComponent() const = 0;
     virtual int monochromeBitsPerComponent() const = 0;
     virtual PointerDeviceType pointer() const = 0;
     virtual bool threeDEnabled() const = 0;
@@ skipping 18 matching lines @@
     bool calculateScreenMediaType(LocalFrame*) const;
     bool calculatePrintMediaType(LocalFrame*) const;
     bool calculateThreeDEnabled(LocalFrame*) const;
     MediaValues::PointerDeviceType calculateLeastCapablePrimaryPointerDeviceType(LocalFrame*) const;
 
 };
 
 } // namespace
 
 #endif // MediaValues_h