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/GrRegionOp.cpp b/src/gpu/ops/GrRegionOp.cpp
index 8d66762..6a3818a 100644
--- a/src/gpu/ops/GrRegionOp.cpp
+++ b/src/gpu/ops/GrRegionOp.cpp
@@ -73,16 +73,14 @@
     }
 
 #if GR_TEST_UTILS
-    SkString dumpInfo() const override {
-        SkString str;
-        str.appendf("# combined: %d\n", fRegions.count());
+    SkString onDumpInfo() const override {
+        SkString str = SkStringPrintf("# combined: %d\n", fRegions.count());
         for (int i = 0; i < fRegions.count(); ++i) {
             const RegionInfo& info = fRegions[i];
             str.appendf("%d: Color: 0x%08x, Region with %d rects\n", i, info.fColor.toBytes_RGBA(),
                         info.fRegion.computeRegionComplexity());
         }
         str += fHelper.dumpInfo();
-        str += INHERITED::dumpInfo();
         return str;
     }
 #endif