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

src/gpu/instanced/InstanceProcessor.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 "InstanceProcessor.h"
 
 #include "GrContext.h"
@@ skipping 1390 matching lines @@
             f->codeAppendf("if (%s != 0) {", fTriangleIsArc.fsIn());
             this->emitArc(f, arcCoords, false, clampArcCoords, opts);
 
             f->codeAppend ("}");
         }
     } else {
         const char* arcTest = fArcTest.fsIn();
         if (arcTest && fBatchInfo.fHasPerspective) {
             // The non-perspective version accounts for fwidth() in the vertex shader.
             // We make sure to take the derivative here, before a neighbor pixel may early accept.
-            f->enableFeature(GrGLSLPPFragmentBuilder::kStandardDerivatives_GLSLFeature);
             f->appendPrecisionModifier(kHigh_GrSLPrecision);
             f->codeAppendf("vec2 arcTest = %s - 0.5 * fwidth(%s);",
                            fArcTest.fsIn(), fArcTest.fsIn());
             arcTest = "arcTest";
         }
         const char* earlyAccept = fEarlyAccept.fsIn() ? fEarlyAccept.fsIn() : "SAMPLE_MASK_ALL";
         f->codeAppendf("if (gl_SampleMaskIn[0] == %s) {", earlyAccept);
         f->overrideSampleCoverage(earlyAccept);
         f->codeAppend ("} else {");
         if (arcTest) {
@@ skipping 692 matching lines @@
 
         case kCorneredRect_FirstIndex: return "basic_round_rect";
         case kCorneredFramedRect_FirstIndex: return "coverage_round_rect";
         case kCorneredRectFanned_FirstIndex: return "mixed_samples_round_rect";
 
         default: return "unknown";
     }
 }
 
 }