Handle the "debug_devtools" build arg in GN builds

chrome/browser/ui/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/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 
 gypi_values = exec_script(
     "//build/gypi_to_gn.py",
     [ rebase_path("../../chrome_browser_ui.gypi") ],
     "scope",
     [ "../../chrome_browser_ui.gypi" ])
 
 static_library("ui") {
   output_name = "browser_ui"
 
   sources = []
   defines = []
   libs = []
 
-  configs += [ "//build/config/compiler:wexit_time_destructors" ]
+  configs += [
+    "//build/config/compiler:wexit_time_destructors",
+    "//third_party/WebKit/public:debug_devtools",
+  ]
 
   # Since browser and browser_ui actually depend on each other,
   # we must omit the dependency from browser_ui to browser.
   # However, this means browser_ui and browser should more or less
   # have the same dependencies. Once browser_ui is untangled from
   # browser, then we can clean up these dependencies.
   public_deps = [
     "//components/dom_distiller/core",
     "//sync",
   ]
@@ skipping 102 matching lines @@
       sources -= [ "views/task_manager_view.cc" ]
     }
   }
   if (!enable_nacl) {
     sources += rebase_path(gypi_values.chrome_browser_ui_nacl_sources,
                            ".", "//chrome")
     deps += [
       #"//native_client/src/trusted/service_runtime/service_runtime.gyp:sel",  TODO(GYP)
     ]
   }
-  if (debug_devtools) {
-    defines += [ "DEBUG_DEVTOOLS=1" ]
-  }
   if (enable_configuration_policy) {
     sources += rebase_path(gypi_values.chrome_browser_ui_policy_sources,
                            ".", "//chrome")
     deps += [ "//components/policy" ]
   }
   if (enable_plugins) {
     sources += rebase_path(gypi_values.chrome_browser_ui_plugin_sources,
                            ".", "//chrome")
     deps += [ "//ppapi:ppapi_ipc" ]
   }
@@ skipping 294 matching lines @@
     "//chrome/browser",
     "//content/public/browser",
     "//content/public/common",
     "//content/test:test_support",
     "//net:test_support",
     "//skia",
     "//testing/gtest",
     "//ui/base",
   ]
 }