add asAShadowBlur for android to drawlooper

src/effects/SkBlurMask.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBlurMask_DEFINED
 #define SkBlurMask_DEFINED
 
@@ skipping 21 matching lines @@
 
     static bool BoxBlur(SkMask* dst, const SkMask& src,
                         SkScalar sigma, SkBlurStyle style, SkBlurQuality quality,
                         SkIPoint* margin = NULL, bool force_quality=false);
 
     // the "ground truth" blur does a gaussian convolution; it's slow
     // but useful for comparison purposes.
     static bool BlurGroundTruth(SkScalar sigma, SkMask* dst, const SkMask& src, SkBlurStyle,
                                 SkIPoint* margin = NULL);
 
+    // If radius > 0, return the corresponding sigma, else return 0
     static SkScalar ConvertRadiusToSigma(SkScalar radius);
+    // If sigma > 0.5, return the corresponding radius, else return 0
+    static SkScalar ConvertSigmaToRadius(SkScalar sigma);
 
     /* Helper functions for analytic rectangle blurs */
 
     /** Look up the intensity of the (one dimnensional) blurred half-plane.
         @param profile The precomputed 1D blur profile; memory allocated by and managed by
                        ComputeBlurProfile below.
         @param loc the location to look up; The lookup will clamp invalid inputs, but
                    meaningful data are available between 0 and blurred_width
         @param blurred_width The width of the final, blurred rectangle
         @param sharp_width The width of the original, unblurred rectangle.
@@ skipping 18 matching lines @@
     */
 
     static void ComputeBlurredScanline(uint8_t* pixels, const uint8_t* profile,
                                        unsigned int width, SkScalar sigma);
 
 
 
 };
 
 #endif