Add constant twoPiDouble/twoPiFloat to MathExtras.h

Source/platform/graphics/filters/FEGaussianBlur.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2005 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) 2010 Igalia, S.L.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 23 matching lines @@
 #include "platform/text/TextStream.h"
 #include "wtf/MathExtras.h"
 #include "wtf/Uint8ClampedArray.h"
 
 #include "SkBlurImageFilter.h"
 
 using namespace std;
 
 static inline float gaussianKernelFactor()
 {
-    return 3 / 4.f * sqrtf(2 * piFloat);
+    return 3 / 4.f * sqrtf(twoPiFloat);
 }
 
 static const unsigned gMaxKernelSize = 1000;
 
 namespace WebCore {
 
 FEGaussianBlur::FEGaussianBlur(Filter* filter, float x, float y)
     : FilterEffect(filter)
     , m_stdX(x)
     , m_stdY(y)
@@ skipping 307 matching lines @@
     return ts;
 }
 
 float FEGaussianBlur::calculateStdDeviation(float radius)
 {
     // Blur radius represents 2/3 times the kernel size, the dest pixel is half of the radius applied 3 times
     return max((radius * 2 / 3.f - 0.5f) / gaussianKernelFactor(), 0.f);
 }
 
 } // namespace WebCore