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

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

Index: src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
diff --git a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
index 5d1ba511b74b5809f5a2e787b44a994b1a2eacb8..e6ecf8c1719ece297c40923846be36c49c198ac9 100644
--- a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
@@ -189,6 +189,10 @@ const char* GrGLSLFragmentShaderBuilder::fragmentPosition() {
     }
 }
 
+const char* GrGLSLFragmentShaderBuilder::distanceVectorName() const {
+    return "fsDistanceVector";
+}
+
 void GrGLSLFragmentShaderBuilder::appendOffsetToSample(const char* sampleIdx, Coordinates coords) {
     SkASSERT(fProgramBuilder->header().fSamplePatternKey);
     SkDEBUGCODE(fUsedProcessorFeatures |= GrProcessor::kSampleLocations_RequiredFeature);