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

src/core/SkNormalSource.cpp

Index: src/core/SkNormalSource.cpp
diff --git a/src/core/SkNormalSource.cpp b/src/core/SkNormalSource.cpp
index 421f56459d0a4c0cf75cd17719ab119f215f44ff..7a4bb2de59ea7797d0bb087c8a196cfcadb82561 100644
--- a/src/core/SkNormalSource.cpp
+++ b/src/core/SkNormalSource.cpp
@@ -385,6 +385,8 @@ public:
         : fType(type)
         , fWidth(width)
         , fHeight(height) {
+        fUsesDistanceVectorField = true;
+
         this->initClassID<NormalBevelFP>();
     }
 
@@ -395,7 +397,15 @@ public:
         void emitCode(EmitArgs& args) override {
             GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
 
-            fragBuilder->codeAppendf("%s = vec4(0, 0, 1, 0);", args.fOutputColor);
+            fragBuilder->codeAppendf("if (%s == vec2(0.0, 0.0)) {",
+                    fragBuilder->distanceVectorName());
+            fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, 1.0, 0.0));",
+                    args.fOutputColor);
+            fragBuilder->codeAppend( "} else {");
+            // TODO (dvonbeck): emit normals according to bevel type and distance vector
+            fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, 1.0, 0.0));",
+                    args.fOutputColor);
+            fragBuilder->codeAppend( "}");
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,