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/effects/generated/GrMixerEffect.cpp b/src/gpu/effects/generated/GrMixerEffect.cpp
index 11bc398..dcb9566 100644
--- a/src/gpu/effects/generated/GrMixerEffect.cpp
+++ b/src/gpu/effects/generated/GrMixerEffect.cpp
@@ -25,8 +25,8 @@
         (void)_outer;
         auto weight = _outer.weight;
         (void)weight;
-        weightVar =
-                args.fUniformHandler->addUniform(kFragment_GrShaderFlag, kHalf_GrSLType, "weight");
+        weightVar = args.fUniformHandler->addUniform(&_outer, kFragment_GrShaderFlag,
+                                                     kHalf_GrSLType, "weight");
         SkString _input1278 = SkStringPrintf("%s", args.fInputColor);
         SkString _sample1278;
         _sample1278 = this->invokeChild(_outer.fp0_index, _input1278.c_str(), args);