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..0ebd3188e37a5d7864d8c02c998f05d9c5cdd9f5 100644
--- a/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
+++ b/src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp
@@ -189,6 +189,20 @@ const char* GrGLSLFragmentShaderBuilder::fragmentPosition() {
     }
 }
 
+bool GrGLSLFragmentShaderBuilder::hasDistanceVectorOutput() const {
+    return !fDistanceVectorOutput.isEmpty();
+}
+
+void GrGLSLFragmentShaderBuilder::enableDistanceVector(const SkString& name) {
+    SkASSERT(!this->hasDistanceVectorOutput());
+    fDistanceVectorOutput = name;
+}
+
+const char* GrGLSLFragmentShaderBuilder::distanceVectorName() const {
+    SkASSERT(this->hasDistanceVectorOutput());
+    return fDistanceVectorOutput.c_str();
+}
+
 void GrGLSLFragmentShaderBuilder::appendOffsetToSample(const char* sampleIdx, Coordinates coords) {
     SkASSERT(fProgramBuilder->header().fSamplePatternKey);
     SkDEBUGCODE(fUsedProcessorFeatures |= GrProcessor::kSampleLocations_RequiredFeature);