Fix attributes types on AnalyserNode as specification of web audio.

Source/modules/webaudio/RealtimeAnalyser.h

 /*
  * 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 27 matching lines @@
 class RealtimeAnalyser FINAL {
     WTF_MAKE_NONCOPYABLE(RealtimeAnalyser);
 public:
     RealtimeAnalyser();
 
     size_t fftSize() const { return m_fftSize; }
     bool setFftSize(size_t);
 
     unsigned frequencyBinCount() const { return m_fftSize / 2; }
 
-    void setMinDecibels(float k) { m_minDecibels = k; }
-    float minDecibels() const { return static_cast<float>(m_minDecibels); }
+    void setMinDecibels(double k) { m_minDecibels = k; }
+    double minDecibels() const { return m_minDecibels; }
 
-    void setMaxDecibels(float k) { m_maxDecibels = k; }
-    float maxDecibels() const { return static_cast<float>(m_maxDecibels); }
+    void setMaxDecibels(double k) { m_maxDecibels = k; }
+    double maxDecibels() const { return m_maxDecibels; }
 
-    void setSmoothingTimeConstant(float k) { m_smoothingTimeConstant = k; }
-    float smoothingTimeConstant() const { return static_cast<float>(m_smoothingTimeConstant); }
+    void setSmoothingTimeConstant(double k) { m_smoothingTimeConstant = k; }
+    double smoothingTimeConstant() const { return m_smoothingTimeConstant; }
 
     void getFloatFrequencyData(Float32Array*);
     void getByteFrequencyData(Uint8Array*);
     void getFloatTimeDomainData(Float32Array*);
     void getByteTimeDomainData(Uint8Array*);
 
     // The audio thread writes input data here.
     void writeInput(AudioBus*, size_t framesToProcess);
 
     static const double DefaultSmoothingTimeConstant;
@@ skipping 22 matching lines @@
     double m_smoothingTimeConstant;
 
     // The range used when converting when using getByteFrequencyData().
     double m_minDecibels;
     double m_maxDecibels;
 };
 
 } // namespace WebCore
 
 #endif // RealtimeAnalyser_h