re-re-land of skslc now automatically turns on derivatives support

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLSLFragmentShaderBuilder.h"
 #include "GrRenderTarget.h"
 #include "GrRenderTargetPriv.h"
@@ skipping 78 matching lines @@
     fSubstageIndices.push_back(0);
 #ifdef SK_DEBUG
     fUsedProcessorFeatures = GrProcessor::kNone_RequiredFeatures;
     fHasReadDstColor = false;
 #endif
 }
 
 bool GrGLSLFragmentShaderBuilder::enableFeature(GLSLFeature feature) {
     const GrGLSLCaps& glslCaps = *fProgramBuilder->glslCaps();
     switch (feature) {
-        case kStandardDerivatives_GLSLFeature:
-            if (!glslCaps.shaderDerivativeSupport()) {
-                return false;
-            }
-            if (const char* extension = glslCaps.shaderDerivativeExtensionString()) {
-                this->addFeature(1 << kStandardDerivatives_GLSLFeature, extension);
-            }
-            return true;
         case kPixelLocalStorage_GLSLFeature:
             if (glslCaps.pixelLocalStorageSize() <= 0) {
                 return false;
             }
             this->addFeature(1 << kPixelLocalStorage_GLSLFeature,
                              "GL_EXT_shader_pixel_local_storage");
             return true;
         case kMultisampleInterpolation_GLSLFeature:
             if (!glslCaps.multisampleInterpolationSupport()) {
                 return false;
@@ skipping 271 matching lines @@
     fMangleString.appendf("_c%d", fSubstageIndices[fSubstageIndices.count() - 2]);
 }
 
 void GrGLSLFragmentShaderBuilder::onAfterChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 2);
     fSubstageIndices.pop_back();
     fSubstageIndices.back()++;
     int removeAt = fMangleString.findLastOf('_');
     fMangleString.remove(removeAt, fMangleString.size() - removeAt);
 }