Got RelaxedPrecision decorations working again in SPIR-V, and removed
no-longer-needed old-style precision handling code.

Bug: skia:8829
Change-Id: I72fc2ee2a305c9c72a3efa92dd44d18239eabaf2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/198169
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/gpu/effects/GrAARectEffect.cpp b/src/gpu/effects/GrAARectEffect.cpp
index 2a4acf1a..649bb7c 100644
--- a/src/gpu/effects/GrAARectEffect.cpp
+++ b/src/gpu/effects/GrAARectEffect.cpp
@@ -28,7 +28,7 @@
         (void)rect;
         prevRect = float4(-1.0);
         fRectUniformVar = args.fUniformHandler->addUniform(
-                kFragment_GrShaderFlag, kFloat4_GrSLType, kDefault_GrSLPrecision, "rectUniform");
+                kFragment_GrShaderFlag, kFloat4_GrSLType, "rectUniform");
         fragBuilder->codeAppendf(
                 "float4 prevRect = float4(%f, %f, %f, %f);\nhalf alpha;\n@switch (%d) {\n    case "
                 "0:\n    case 2:\n        alpha = half(all(greaterThan(float4(sk_FragCoord.xy, "