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/GrFillRectOp.cpp b/src/gpu/ops/GrFillRectOp.cpp
index 28322f5..d46df45 100644
--- a/src/gpu/ops/GrFillRectOp.cpp
+++ b/src/gpu/ops/GrFillRectOp.cpp
@@ -121,9 +121,8 @@
     }
 
 #if GR_TEST_UTILS
-    SkString dumpInfo() const override {
-        SkString str;
-        str.appendf("# draws: %u\n", fQuads.count());
+    SkString onDumpInfo() const override {
+        SkString str = SkStringPrintf("# draws: %u\n", fQuads.count());
         str.appendf("Device quad type: %u, local quad type: %u\n",
                     (uint32_t) fQuads.deviceQuadType(), (uint32_t) fQuads.localQuadType());
         str += fHelper.dumpInfo();
@@ -135,7 +134,6 @@
                                   info.fColor, info.fAAFlags);
             i++;
         }
-        str += INHERITED::dumpInfo();
         return str;
     }
 #endif