Move debug_devtools to a buildflag_header.

chrome/browser/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.
 
 if (!is_android) {
   import("//build/config/features.gni")
   import("//chrome/common/features.gni")
   import("//tools/grit/grit_rule.gni")
 }
 
@@ skipping 37 matching lines @@
     "devtools_network_upload_data_stream.h",
     "devtools_protocol.cc",
     "devtools_protocol.h",
   ]
   sources += get_target_outputs(":devtools_protocol_constants")
 
   configs += [
     "//build/config/compiler:no_size_t_to_int_warning",
     "//build/config/compiler:wexit_time_destructors",
     "//build/config:precompiled_headers",
-    "//third_party/WebKit/public:debug_devtools",
   ]
 
   deps = [
     ":devtools_protocol_constants",
     "//base",
     "//content/public/browser",
     "//net",
+    "//third_party/WebKit/public:features",
     "//ui/events:dom_keycode_converter",
   ]
 
   if (!is_android) {
     deps += [
       "//chrome:extra_resources",
       "//chrome:resources",
       "//chrome:strings",
       "//chrome/app/theme:theme_resources",
       "//chrome/common",
@@ skipping 56 matching lines @@
       "remote_debugging_server.h",
     ]
     if (enable_service_discovery) {
       sources += [
         "device/cast_device_provider.cc",
         "device/cast_device_provider.h",
       ]
     }
   }
 }