[tracing] Move GN/gyp build files under trace_event

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index f1034466a65dbb033103fd4743edf6b288509322..1a2ce49d8c458022cc33bc41ee4409ef7dc0e0b1 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1248,15 +1248,6 @@ test("base_unittests") {
     "timer/mock_timer_unittest.cc",
     "timer/timer_unittest.cc",
     "tools_sanity_unittest.cc",
-    "trace_event/memory_dump_manager_unittest.cc",
-    "trace_event/process_memory_maps_dump_provider_unittest.cc",
-    "trace_event/process_memory_totals_dump_provider_unittest.cc",
-    "trace_event/trace_event_argument_unittest.cc",
-    "trace_event/trace_event_memory_unittest.cc",
-    "trace_event/trace_event_synthetic_delay_unittest.cc",
-    "trace_event/trace_event_system_stats_monitor_unittest.cc",
-    "trace_event/trace_event_unittest.cc",
-    "trace_event/trace_event_win_unittest.cc",
     "tracked_objects_unittest.cc",
     "tuple_unittest.cc",
     "values_unittest.cc",
@@ -1294,6 +1285,7 @@ test("base_unittests") {
     "//base/test:test_support",
     "//base/third_party/dynamic_annotations",
     "//base/third_party/nspr",
+    "//base/trace_event:trace_event_unittests",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/icu",