Add granular file tracing.

base/trace_event/BUILD.gn

 # 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",
     "memory_dump_provider.cc",
     "memory_dump_provider.h",
     "memory_dump_request_args.h",
     "process_memory_dump.cc",
     "process_memory_dump.h",
     "process_memory_maps.cc",
     "process_memory_maps.h",
     "process_memory_maps_dump_provider.cc",
     "process_memory_maps_dump_provider.h",
     "process_memory_totals.cc",
     "process_memory_totals.h",
     "process_memory_totals_dump_provider.cc",
     "process_memory_totals_dump_provider.h",
+    "scoped_file_trace.cc",
+    "scoped_file_trace.h",
     "trace_event.h",
     "trace_event_android.cc",
     "trace_event_argument.cc",
     "trace_event_argument.h",
     "trace_event_etw_export_win.cc",
     "trace_event_etw_export_win.h",
     "trace_event_impl.cc",
     "trace_event_impl.h",
     "trace_event_impl_constants.cc",
     "trace_event_memory.cc",
@@ skipping 57 matching lines @@
     "trace_event_unittest.cc",
     "trace_event_win_unittest.cc",
   ]
 
   deps = [
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 }