DevTools: introduce "Track CSS Usage" experiment

third_party/WebKit/Source/devtools/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/config/features.gni")
 import("//third_party/WebKit/public/public_features.gni")
 import("//third_party/WebKit/Source/core/core.gni")
 
 devtools_embedder_scripts = [
   "front_end/devtools_compatibility.js",
@@ skipping 389 matching lines @@
   "front_end/cm_modes/clojure.js",
   "front_end/cm_modes/DefaultCodeMirrorMimeMode.js",
 ]
 devtools_components_lazy_js_files = [
   "front_end/components_lazy/filmStripDialog.css",
   "front_end/components_lazy/filmStripView.css",
   "front_end/components_lazy/CookiesTable.js",
   "front_end/components_lazy/FilmStripModel.js",
   "front_end/components_lazy/FilmStripView.js",
   "front_end/components_lazy/LineLevelProfile.js",
+  "front_end/components_lazy/LineMarkingProfile.js",
 ]
 devtools_console_js_files = [
   "front_end/console/consoleView.css",
   "front_end/console/ConsoleContextSelector.js",
   "front_end/console/ConsolePanel.js",
   "front_end/console/ConsolePrompt.js",
   "front_end/console/ConsoleView.js",
   "front_end/console/ConsoleViewMessage.js",
 ]
 devtools_devices_js_files = [
@@ skipping 730 matching lines @@
     deps = [
       ":frontend_protocol_sources",
       ":supported_css_properties",
     ]
     sources = generated_scripts
     outputs = [
       "$resources_out_debug_dir/{{source_file_part}}",
     ]
   }
 }