Add support for object creation/snapshot/deletion events

- Bring back some previously deleted macros and helper types.
- Automatically inject base_type information into snapshot events,
  to allow simpler tracking of polymorphic object types.
- Fix JSON formatting of pointer values (they were serializing as bool).

Bug: skia:
Change-Id: Iac7803f72ce5396ffd2fbcb5a36d76745c5e3f3e
Reviewed-on: https://skia-review.googlesource.com/28220
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/gn/tests.gni b/gn/tests.gni
index 03138d5..3edb3e3 100644
--- a/gn/tests.gni
+++ b/gn/tests.gni
@@ -252,6 +252,7 @@
   "$_tests/TLSTest.cpp",
   "$_tests/TopoSortTest.cpp",
   "$_tests/TraceMemoryDumpTest.cpp",
+  "$_tests/TracingTest.cpp",
   "$_tests/TransferPixelsTest.cpp",
   "$_tests/TypefaceTest.cpp",
   "$_tests/UnicodeTest.cpp",