tracing: split out the CategoryRegistry from the TraceLog

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index a3e3205eae9f137c15c774fdff736a88124201f8..d6aad359b101552b9922c90e5bc76f7c9fde9208 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -898,6 +898,8 @@ component("base") {
     "trace_event/auto_open_close_event.h",
     "trace_event/blame_context.cc",
     "trace_event/blame_context.h",
+    "trace_event/category_registry.cc",
+    "trace_event/category_registry.h",
     "trace_event/common/trace_event_common.h",
     "trace_event/heap_profiler.h",
     "trace_event/heap_profiler_allocation_context.cc",
@@ -939,6 +941,7 @@ component("base") {
     "trace_event/process_memory_totals.h",
     "trace_event/trace_buffer.cc",
     "trace_event/trace_buffer.h",
+    "trace_event/trace_category.h",
     "trace_event/trace_config.cc",
     "trace_event/trace_config.h",
     "trace_event/trace_event.h",
@@ -1982,6 +1985,7 @@ test("base_unittests") {
     "trace_event/memory_allocator_dump_unittest.cc",
     "trace_event/memory_dump_manager_unittest.cc",
     "trace_event/process_memory_dump_unittest.cc",
+    "trace_event/trace_category_unittest.cc",
     "trace_event/trace_config_unittest.cc",
     "trace_event/trace_event_argument_unittest.cc",
     "trace_event/trace_event_synthetic_delay_unittest.cc",