[DevTools] Explicitly add Tethering domain to browser protocol.

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.
 
 action("devtools_protocol_constants") {
   script = "//content/public/browser/devtools_protocol_constants_generator.py"
 
   blink_protocol = "//third_party/WebKit/Source/devtools/protocol.json"
-  inputs = [ blink_protocol ]
+  browser_protocol = "//content/browser/devtools/browser_protocol.json"
+  inputs = [ blink_protocol, browser_protocol ]
   outputs = [
     "$target_gen_dir/devtools_protocol_constants.cc",
     "$target_gen_dir/devtools_protocol_constants.h",
   ]
 
   args = [ "chrome" ]
   args += rebase_path(outputs, root_build_dir)
   args += [ rebase_path(blink_protocol, root_build_dir) ]
+  args += [ rebase_path(browser_protocol, root_build_dir) ]
 }
 
 # GYP version: chrome/chrome_debugger.gypi:debugger
 static_library("devtools") {
   # Note: new sources and deps should be generally added in (!is_android) below.
   sources = [
     "chrome_devtools_manager_delegate.cc",
     "chrome_devtools_manager_delegate.h",
     "devtools_network_conditions.cc",
     "devtools_network_conditions.h",
@@ skipping 85 matching lines @@
       "devtools_toggle_action.h",
       "devtools_ui_bindings.cc",
       "devtools_ui_bindings.h",
       "devtools_window.cc",
       "devtools_window.h",
       "remote_debugging_server.cc",
       "remote_debugging_server.h"
     ]
   }
 }