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

src/gpu/batches/GrAAConvexPathRenderer.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAAConvexPathRenderer.h"
 
 #include "GrAAConvexTessellator.h"
@@ skipping 561 matching lines @@
 
             // emit transforms
             this->emitTransforms(vertBuilder,
                                  varyingHandler,
                                  uniformHandler,
                                  gpArgs->fPositionVar,
                                  qe.inPosition()->fName,
                                  qe.localMatrix(),
                                  args.fFPCoordTransformHandler);
 
-            SkAssertResult(fragBuilder->enableFeature(
-                    GrGLSLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));
             fragBuilder->codeAppendf("float edgeAlpha;");
 
             // keep the derivative instructions outside the conditional
             fragBuilder->codeAppendf("vec2 duvdx = dFdx(%s.xy);", v.fsIn());
             fragBuilder->codeAppendf("vec2 duvdy = dFdy(%s.xy);", v.fsIn());
             fragBuilder->codeAppendf("if (%s.z > 0.0 && %s.w > 0.0) {", v.fsIn(), v.fsIn());
             // today we know z and w are in device space. We could use derivatives
             fragBuilder->codeAppendf("edgeAlpha = min(min(%s.z, %s.w) + 0.5, 1.0);", v.fsIn(),
                                      v.fsIn());
             fragBuilder->codeAppendf ("} else {");
@@ skipping 416 matching lines @@
 
 DRAW_BATCH_TEST_DEFINE(AAConvexPathBatch) {
     GrColor color = GrRandomColor(random);
     SkMatrix viewMatrix = GrTest::TestMatrixInvertible(random);
     SkPath path = GrTest::TestPathConvex(random);
 
     return new AAConvexPathBatch(color, viewMatrix, path);
 }
 
 #endif