Fixed error when normal.z = 1 in GPUs with binary16 floats

src/core/SkNormalSource.cpp

Index: src/core/SkNormalSource.cpp
diff --git a/src/core/SkNormalSource.cpp b/src/core/SkNormalSource.cpp
index 52bb4adaa70092504a58bc4f17ecd825f6b4988a..03c1a3a80c39e31caea8b412eb0fc1634c41044b 100644
--- a/src/core/SkNormalSource.cpp
+++ b/src/core/SkNormalSource.cpp
@@ -109,7 +109,7 @@ public:
             // transforming all the normals here!
 
             // If there's no x & y components, return (0, 0, +/- 1) instead to avoid division by 0
-            fragBuilder->codeAppend( "if (abs(normal.z) > 0.9999) {");
+            fragBuilder->codeAppend( "if (abs(normal.z) > 0.999) {");
             fragBuilder->codeAppendf("    %s = normalize(vec4(0.0, 0.0, normal.z, 0.0));",
                     args.fOutputColor);
             // Else, Normalizing the transformed X and Y, while keeping constant both Z and the