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

src/gpu/glsl/GrGLSLFragmentProcessor.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 "GrGLSLFragmentProcessor.h"
 #include "GrFragmentProcessor.h"
 #include "GrProcessor.h"
@@ skipping 89 matching lines @@
     fragBuilder->codeAppendf("// Child Index %d (mangle: %s): %s\n", childIndex,
                              fragBuilder->getMangleString().c_str(), childProc.name());
     EmitArgs childArgs(fragBuilder,
                        args.fUniformHandler,
                        args.fGLSLCaps,
                        childProc,
                        outputColor,
                        inputColor,
                        childCoords,
                        childTexSamplers,
-                       childBufferSamplers);
+                       childBufferSamplers,
+                       args.fGpImplementsDistanceVector);
     this->childProcessor(childIndex)->emitCode(childArgs);
     fragBuilder->codeAppend("}\n");
 
     fragBuilder->onAfterChildProcEmitCode();
 }