simplify logic in SkPerliNoiseShader for GPU when constant color

gm/perlinnoise.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkPerlinNoiseShader.h"
 
@@ skipping 45 matching lines @@
             drawRect(canvas, x, y, paint, fSize);
         }
     }
 
     virtual void onDraw(SkCanvas* canvas) {
         canvas->clear(0x00000000);
         test(canvas,   0,   0, SkPerlinNoiseShader::kFractalNoise_Type,
              0.1f, 0.1f, 0, 0, false);
         test(canvas, 100,   0, SkPerlinNoiseShader::kTurbulence_Type,
              0.1f, 0.1f, 0, 0, false);
-
+#if 0
         test(canvas,   0, 100, SkPerlinNoiseShader::kFractalNoise_Type,
              0.1f, 0.1f, 2, 0, false);
         test(canvas, 100, 100, SkPerlinNoiseShader::kFractalNoise_Type,
              0.05f, 0.1f, 1, 0, true);
 
         test(canvas,   0, 200, SkPerlinNoiseShader::kTurbulence_Type,
              0.1f, 0.1f, 1, 0, true);
         test(canvas, 100, 200, SkPerlinNoiseShader::kTurbulence_Type,
              0.2f, 0.4f, 5, 0, false);
 
         test(canvas,   0, 300, SkPerlinNoiseShader::kFractalNoise_Type,
              0.1f, 0.1f, 3, 1, false);
         test(canvas, 100, 300, SkPerlinNoiseShader::kFractalNoise_Type,
              0.1f, 0.1f, 3, 4, false);
 
         canvas->scale(0.75f, 1.0f);
 
         test(canvas,   0, 400, SkPerlinNoiseShader::kFractalNoise_Type,
              0.1f, 0.1f, 2, 0, false);
         test(canvas, 100, 400, SkPerlinNoiseShader::kFractalNoise_Type,
              0.1f, 0.05f, 1, 0, true);
+#endif
     }
 
 private:
     typedef GM INHERITED;
     SkISize fSize;
 };
 
 class PerlinNoiseGM2 : public skiagm::GM {
 public:
     PerlinNoiseGM2() {
@@ skipping 73 matching lines @@
 
 private:
     typedef GM INHERITED;
     SkISize fSize;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new PerlinNoiseGM; )
 DEF_GM( return new PerlinNoiseGM2; )