[inspector] use own version of third_party/inspector_protocol

third_party/inspector_protocol/inspector_protocol.gni

 # Copyright 2016 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.
 
 # This template will generate inspector protocol source code. The code will
 # not be compiled, use get_target_outputs(<name>) to compile them.
 #
 # Inputs
 #
 #   config_file  (required)
 #       Path to json file specifying inspector protocol configuration.
 #
 #   out_dir  (required)
 #       Path to put the generated files in. It must be inside output or
 #       generated file directory.
 #
 #   outputs (required)
 #       Files generated. Relative to out_dir.
 #
 #   inputs  (optional)
 #       Extra inputs specified by the config file.
 template("inspector_protocol_generate") {
   assert(defined(invoker.config_file))
   assert(defined(invoker.out_dir))
   assert(defined(invoker.outputs))
-
-  inspector_protocol_dir =
-      "//third_party/WebKit/Source/platform/inspector_protocol"
+  assert(defined(invoker.inspector_protocol_dir))
+  inspector_protocol_dir = invoker.inspector_protocol_dir
 
   action(target_name) {
     script = "$inspector_protocol_dir/CodeGenerator.py"
 
     inputs = [
       invoker.config_file,
       "$inspector_protocol_dir/lib/Allocator_h.template",
       "$inspector_protocol_dir/lib/Array_h.template",
       "$inspector_protocol_dir/lib/BackendCallback_h.template",
       "$inspector_protocol_dir/lib/Collections_h.template",
@@ skipping 34 matching lines @@
                             "abspath")
 
     forward_variables_from(invoker,
                            [
                              "visibility",
                              "deps",
                              "public_deps",
                            ])
   }
 }