Revert of [mojo-bindings] Use Watch API instead of MessagePumpMojo

mojo/public/cpp/bindings/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.
 
 source_set("bindings") {
   sources = [
     "array.h",
     "associated_binding.h",
     "associated_group.h",
     "associated_interface_ptr.h",
@@ skipping 83 matching lines @@
 
   public_deps = [
     ":callback",
     "//base",
     "//ipc:param_traits",
     "//mojo/public/cpp/system",
   ]
 
   deps = [
     "//base",
+    "//mojo/message_pump",
     "//mojo/public/interfaces/bindings:bindings_cpp_sources",
   ]
 }
 
 source_set("callback") {
   sources = [
     "callback.h",
     "lib/callback_internal.h",
     "lib/shared_data.h",
     "lib/shared_ptr.h",
     "lib/template_util.h",
   ]
 
   deps = [
     "//base",
     "//mojo/public/cpp/system",
   ]
 }