Update GrPaint APIs to reflect lack of multiple color processors.

Change-Id: Ic7799b3c5f4294cba9ff72f8c11a2ad285ab189f
Bug: skia:10217
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/304738
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/tools/gpu/TestOps.cpp b/tools/gpu/TestOps.cpp
index e0a195f..cfd6815 100644
--- a/tools/gpu/TestOps.cpp
+++ b/tools/gpu/TestOps.cpp
@@ -230,7 +230,7 @@
                                    const SkRect& localRect,
                                    const SkMatrix& localM) {
     GrPaint paint;
-    paint.addColorFragmentProcessor(std::move(fp));
+    paint.setColorFragmentProcessor(std::move(fp));
     return TestRectOp::Make(context, std::move(paint), drawRect, localRect, localM);
 }