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/GrLinearGradientLayout.cpp b/src/gpu/gradients/generated/GrLinearGradientLayout.cpp
index 63d4f7b..62d92bd 100644
--- a/src/gpu/gradients/generated/GrLinearGradientLayout.cpp
+++ b/src/gpu/gradients/generated/GrLinearGradientLayout.cpp
@@ -54,7 +54,7 @@
     return std::make_unique<GrLinearGradientLayout>(*this);
 }
 #if GR_TEST_UTILS
-SkString GrLinearGradientLayout::dumpInfo() const { return SkStringPrintf("LinearGradientLayout"); }
+SkString GrLinearGradientLayout::onDumpInfo() const { return SkString(); }
 #endif
 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrLinearGradientLayout);
 #if GR_TEST_UTILS