Add constant twoPiDouble/twoPiFloat to MathExtras.h

Source/platform/transforms/AffineTransform.cpp

Index: Source/platform/transforms/AffineTransform.cpp
diff --git a/Source/platform/transforms/AffineTransform.cpp b/Source/platform/transforms/AffineTransform.cpp
index 44517294e4dadca823d55a9f4211f5c872bee1b1..33eb7aa379358969bc8b26e2b38e9e1adb543408 100644
--- a/Source/platform/transforms/AffineTransform.cpp
+++ b/Source/platform/transforms/AffineTransform.cpp
@@ -322,14 +322,14 @@ void AffineTransform::blend(const AffineTransform& from, double progress)
     }
 
     // Don't rotate the long way around.
-    srA.angle = fmod(srA.angle, 2 * piDouble);
-    srB.angle = fmod(srB.angle, 2 * piDouble);
+    srA.angle = fmod(srA.angle, twoPiDouble);
+    srB.angle = fmod(srB.angle, twoPiDouble);
 
     if (fabs(srA.angle - srB.angle) > piDouble) {
         if (srA.angle > srB.angle)
-            srA.angle -= piDouble * 2;
+            srA.angle -= twoPiDouble;
         else
-            srB.angle -= piDouble * 2;
+            srB.angle -= twoPiDouble;
     }
 
     srA.scaleX += progress * (srB.scaleX - srA.scaleX);