Update GrOp subclasses to use `onDumpInfo` for info dumping.

This is meant to parallel the changes in http://review.skia.org/309793,
but for GrOps. The base-class info is automatically appended without
subclasses manually calling `append(INHERITED::dumpInfo())`.

Change-Id: Ic815305feeeca07385687af5703f0dd88a008f9f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/309879
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
diff --git a/src/gpu/ops/GrTriangulatingPathRenderer.cpp b/src/gpu/ops/GrTriangulatingPathRenderer.cpp
index 15baa45..f0a2a45 100644
--- a/src/gpu/ops/GrTriangulatingPathRenderer.cpp
+++ b/src/gpu/ops/GrTriangulatingPathRenderer.cpp
@@ -191,12 +191,9 @@
     }
 
 #if GR_TEST_UTILS
-    SkString dumpInfo() const override {
-        SkString string;
-        string.appendf("Color 0x%08x, aa: %d\n", fColor.toBytes_RGBA(), fAntiAlias);
-        string += fHelper.dumpInfo();
-        string += INHERITED::dumpInfo();
-        return string;
+    SkString onDumpInfo() const override {
+        return SkStringPrintf("Color 0x%08x, aa: %d\n%s",
+                              fColor.toBytes_RGBA(), fAntiAlias, fHelper.dumpInfo().c_str());
     }
 #endif