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/sksl/SkSLHCodeGenerator.cpp b/src/sksl/SkSLHCodeGenerator.cpp
index 4802eb9..0cbb3d0 100644
--- a/src/sksl/SkSLHCodeGenerator.cpp
+++ b/src/sksl/SkSLHCodeGenerator.cpp
@@ -356,7 +356,7 @@
     this->writeMake();
     this->writef("    %s(const %s& src);\n"
                  "#if GR_TEST_UTILS\n"
-                 "    SkString dumpInfo() const override;\n"
+                 "    SkString onDumpInfo() const override;\n"
                  "#endif\n"
                  "    std::unique_ptr<GrFragmentProcessor> clone() const override;\n"
                  "    const char* name() const override { return \"%s\"; }\n",