Add `GrProcessor::onDumpInfo` for subclass info dumps.

This CL also marks `GrProcessor::dumpInfo` as final. This prevents a
subclass from mistakenly overriding `dumpInfo` instead of `onDumpInfo`.

`onDumpInfo` is responsible for providing the same data as `dumpInfo`,
except that the FP name is automatically prepended.

Change-Id: I2b44c30a01bc65e9d88321cc21651a94e20074c6
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/309793
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/gradients/generated/GrSweepGradientLayout.cpp b/src/gpu/gradients/generated/GrSweepGradientLayout.cpp
index 8a81edc..58742ac 100644
--- a/src/gpu/gradients/generated/GrSweepGradientLayout.cpp
+++ b/src/gpu/gradients/generated/GrSweepGradientLayout.cpp
@@ -92,8 +92,8 @@
     return std::make_unique<GrSweepGradientLayout>(*this);
 }
 #if GR_TEST_UTILS
-SkString GrSweepGradientLayout::dumpInfo() const {
-    return SkStringPrintf("SweepGradientLayout(bias=%f, scale=%f)", bias, scale);
+SkString GrSweepGradientLayout::onDumpInfo() const {
+    return SkStringPrintf("(bias=%f, scale=%f)", bias, scale);
 }
 #endif
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrSweepGradientLayout);