[tracing] Move GN/gyp build files under trace_event

base/trace_event/BUILD.gn

-# Copyright (c) 2015 The Chromium Authors. All rights reserved.
+# Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 source_set("trace_event") {
   sources = [
     "memory_allocator_attributes.h",
     "memory_allocator_dump.cc",
     "memory_allocator_dump.h",
     "memory_dump_manager.cc",
     "memory_dump_manager.h",
@@ skipping 44 matching lines @@
   ]
 
   allow_circular_includes_from = [
     "//base/debug",
     "//base/memory",
     "//base/process",
   ]
 
   visibility = [ "//base/*" ]
 }
+
+source_set("trace_event_unittests") {
+  testonly = true
+  sources = [
+    "memory_allocator_dump_unittest.cc",
+    "memory_dump_manager_unittest.cc",
+    "process_memory_maps_dump_provider_unittest.cc",
+    "process_memory_totals_dump_provider_unittest.cc",
+    "trace_event_argument_unittest.cc",
+    "trace_event_memory_unittest.cc",
+    "trace_event_synthetic_delay_unittest.cc",
+    "trace_event_system_stats_monitor_unittest.cc",
+    "trace_event_unittest.cc",
+    "trace_event_win_unittest.cc",
+  ]
+
+  deps = [
+    "//base/test:test_support",
+    "//testing/gmock",
+    "//testing/gtest",
+  ]
+}