Tracking uniform ownership

This is a prerequisite change for the upcoming sample(child, matrix)
function. By itself, this CL doesn't really change anything; it just
adds an ownership tracking feature which sample(child, matrix) depends
on.

Change-Id: I98b12e5fb062a2535af367931e7a932ea9c63a59
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/281337
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/gpu/GrDefaultGeoProcFactory.cpp b/src/gpu/GrDefaultGeoProcFactory.cpp
index fcbb282..4f93238 100644
--- a/src/gpu/GrDefaultGeoProcFactory.cpp
+++ b/src/gpu/GrDefaultGeoProcFactory.cpp
@@ -83,7 +83,8 @@
                     vertBuilder->codeAppendf("half4 color = %s;", gp.fInColor.name());
                 } else {
                     const char* colorUniformName;
-                    fColorUniform = uniformHandler->addUniform(kVertex_GrShaderFlag,
+                    fColorUniform = uniformHandler->addUniform(nullptr,
+                                                               kVertex_GrShaderFlag,
                                                                kHalf4_GrSLType,
                                                                "Color",
                                                                &colorUniformName);
@@ -128,7 +129,8 @@
                 fragBuilder->codeAppendf("%s = half4(1);", args.fOutputCoverage);
             } else {
                 const char* fragCoverage;
-                fCoverageUniform = uniformHandler->addUniform(kFragment_GrShaderFlag,
+                fCoverageUniform = uniformHandler->addUniform(nullptr,
+                                                              kFragment_GrShaderFlag,
                                                               kHalf_GrSLType,
                                                               "Coverage",
                                                               &fragCoverage);