Update SampleAndroidShadows to use algorithm closer to Android OpenGL

src/effects/SkGaussianEdgeShader.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkGaussianEdgeShader.h"
 #include "SkReadBuffer.h"
 #include "SkWriteBuffer.h"
@@ skipping 53 matching lines @@
 
     class GLSLGaussianEdgeFP : public GrGLSLFragmentProcessor {
     public:
         GLSLGaussianEdgeFP() {}
 
         void emitCode(EmitArgs& args) override {
 
             GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
 
             fragBuilder->codeAppendf("vec4 color = %s;", args.fInputColor);
-            fragBuilder->codeAppend("float radius = color.g*64.0;");
+            fragBuilder->codeAppend("float radius = color.r*1024.0 + color.g*64.0;");
             fragBuilder->codeAppend("float pad = color.b*64.0;");
 
             fragBuilder->codeAppendf("float factor = 1.0 - clamp((%s.z - pad)/radius, 0.0, 1.0);",
                                      fragBuilder->distanceVectorName());
             fragBuilder->codeAppend("factor = exp(-factor * factor * 4.0) - 0.018;");
-            fragBuilder->codeAppendf("%s = factor*vec4(0.0, 0.0, 0.0, color.r);", args.fOutputColor);
+            fragBuilder->codeAppendf("%s = factor*vec4(0.0, 0.0, 0.0, color.a);", args.fOutputColor);
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
                            GrProcessorKeyBuilder* b) {
             // only one shader generated currently
             b->add32(0x0);
         }
 
     protected:
         void onSetData(const GrGLSLProgramDataManager& pdman, const GrProcessor& proc) override {}
@@ skipping 51 matching lines @@
     return sk_make_sp<SkGaussianEdgeShaderImpl>();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkGaussianEdgeShader)
 SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkGaussianEdgeShaderImpl)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ///////////////////////////////////////////////////////////////////////////////