DevTools: split protocol.json into files per domain.

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("//tools/grit/grit_rule.gni")
 }
 
 action("devtools_protocol_constants") {
   script = "devtools_protocol_constants_generator.py"
-
-  blink_protocol = "//third_party/WebKit/Source/devtools/protocol.json"
+  deps = [
+    "//third_party/WebKit/Source/core/inspector:protocol_version",
+  ]
+  blink_protocol =
+      "$target_gen_dir/../../../blink/core/inspector/protocol.json"
   browser_protocol = "//content/browser/devtools/browser_protocol.json"
   inputs = [
     blink_protocol,
     browser_protocol,
   ]
   outputs = [
     "$target_gen_dir/devtools_protocol_constants.cc",
     "$target_gen_dir/devtools_protocol_constants.h",
   ]
 
@@ skipping 110 matching lines @@
       "remote_debugging_server.h",
     ]
     if (enable_service_discovery) {
       sources += [
         "device/cast_device_provider.cc",
         "device/cast_device_provider.h",
       ]
     }
   }
 }