GrFP can express distance vector field req., program builder declares variable for it

src/gpu/GrFragmentProcessor.cpp

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "GrFragmentProcessor.h"
 #include "GrCoordTransform.h"
 #include "GrInvariantOutput.h"
@@ skipping 88 matching lines @@
     if (!child->fTextureAccesses.empty()) {
         fTextureAccesses.push_back_n(child->fTextureAccesses.count(),
                                      child->fTextureAccesses.begin());
     }
 
     this->combineRequiredFeatures(*child);
 
     if (child->usesLocalCoords()) {
         fUsesLocalCoords = true;
     }
+    if (child->usesDistanceVectorField()) {
+        fUsesDistanceVectorField = true;
+    }
 
     int index = fChildProcessors.count();
     fChildProcessors.push_back(child.release());
 
     return index;
 }
 
 void GrFragmentProcessor::notifyRefCntIsZero() const {
     // See comment above GrProgramElement for a detailed explanation of why we do this.
     for (int i = 0; i < fChildProcessors.count(); ++i) {
@@ skipping 291 matching lines @@
     } else {
         series += firstIdx;
         cnt -= firstIdx;
     }
 
     if (1 == cnt) {
         return series[0];
     }
     return sk_sp<GrFragmentProcessor>(new SeriesFragmentProcessor(series, cnt));
 }