Convert FieldTrialActivated to use mojo.

chrome/common/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/buildflag_header.gni")
 import("//build/util/process_version.gni")
 import("//chrome/common/features.gni")
 import("//chrome/process_version_rc_template.gni")  # For branding_file_path.
 import("//extensions/features/features.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
@@ skipping 647 matching lines @@
   configs += [ "//build/config/compiler:wexit_time_destructors" ]
 
   deps = [
     ":constants",
     "//base",
   ]
 }
 
 mojom("mojo_bindings") {
   sources = [
+    "field_trial_recorder.mojom",
     "network_diagnostics.mojom",
     "resource_usage_reporter.mojom",
     "shell_handler_win.mojom",
   ]
 
   public_deps = [
     "//url/mojo:url_mojom_gurl",
   ]
 }