Use mojo from the PDF extension instead of using an extension API.

extensions/common/api/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.
 
 import("//build/config/features.gni")
 import("//build/json_schema_api.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 assert(enable_extensions)
 
@@ skipping 15 matching lines @@
   "dns.idl",
   "events.json",
   "extensions_manifest_types.json",
   "extension_options_internal.idl",
   "extension_view_internal.json",
   "extension_types.json",
   "guest_view_internal.json",
   "management.json",
   "hid.idl",
   "idle.json",
-  "mime_handler_private.idl",
   "mime_handler_view_guest_internal.json",
   "mojo_private.idl",
   "networking_private.idl",
   "power.idl",
   "printer_provider.idl",
   "printer_provider_internal.idl",
   "runtime.json",
   "serial.idl",
   "socket.idl",
   "sockets_tcp.idl",
@@ skipping 64 matching lines @@
   deps = [
     ":api",
     "//device/serial",
     "//extensions/common/api/cast_channel:cast_channel_proto",
     "//skia",
   ]
 
   # Inherit uncompiled_sources, uncompiled_bundle_schema_sources, and
   # root_namespace.
 }