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/GrMixerEffect.cpp b/src/gpu/effects/GrMixerEffect.cpp
index 6e79f51..fb0e50e 100644
--- a/src/gpu/effects/GrMixerEffect.cpp
+++ b/src/gpu/effects/GrMixerEffect.cpp
@@ -24,8 +24,8 @@
         (void)_outer;
         auto weight = _outer.weight();
         (void)weight;
-        fWeightVar = args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kHalf_GrSLType,
-                                                      kDefault_GrSLPrecision, "weight");
+        fWeightVar =
+                args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kHalf_GrSLType, "weight");
         SkString _input0 = SkStringPrintf("%s", args.fInputColor);
         SkString _child0("_child0");
         this->emitChild(_outer.fp0_index(), _input0.c_str(), &_child0, args);