Add constant twoPiDouble/twoPiFloat to MathExtras.h

Source/platform/audio/EqualPowerPanner.cpp

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 83 matching lines @@
             // sourceL -> destL and "equal-power pan" sourceR as in mono case
             // by transforming the "azimuth" value from -90 -> 0 degrees into the range -90 -> +90.
             desiredPanPosition = (azimuth + 90) / 90;
         } else { // from 0 -> +90
             // sourceR -> destR and "equal-power pan" sourceL as in mono case
             // by transforming the "azimuth" value from 0 -> +90 degrees into the range -90 -> +90.
             desiredPanPosition = azimuth / 90;
         }
     }
 
-    desiredGainL = cos(0.5 * piDouble * desiredPanPosition);
-    desiredGainR = sin(0.5 * piDouble * desiredPanPosition);
+    desiredGainL = cos(piOverTwoDouble * desiredPanPosition);
+    desiredGainR = sin(piOverTwoDouble * desiredPanPosition);
 
     // Don't de-zipper on first render call.
     if (m_isFirstRender) {
         m_isFirstRender = false;
         m_gainL = desiredGainL;
         m_gainR = desiredGainR;
     }
 
     // Cache in local variables.
     double gainL = m_gainL;
@@ skipping 34 matching lines @@
         }
     }
 
     m_gainL = gainL;
     m_gainR = gainR;
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)