Add option to export tracing events to ETW.

base/trace_event/etw_manifest/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.
+
+assert(is_win, "This only runs on Windows.")
+
+# Makes the .h/.rc files from the .man file.
+action("chrome_events_win") {
+  visibility = [
+    "//base/trace_event/*",
+    "//chrome:main_dll",
+  ]
+  script = "build/message_compiler.py"
+
+  sources = [
+    "chrome_events_win.man",
+  ]
+
+  outputs = [
+    "$target_gen_dir/chrome_events_win.h",
+    "$target_gen_dir/chrome_events_win.rc",
+  ]
+
+  args = [
+    # Where to put the header.
+    "-h",
+    rebase_path("$target_gen_dir", root_build_dir),
+
+    # Where to put the .rc file.
+    "-r",
+    rebase_path("$target_gen_dir", root_build_dir),
+
+    # Generate the user-mode code.
+    "-um",
+    rebase_path("chrome_events_win.man", root_build_dir),
+  ]
+}