Cleanup: Remove most enable_extensions logic in chrome/ extensions code.

chrome/common/extensions/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/json_schema_api.gni")
 import("schemas.gni")
 
+assert(enable_extensions)
+
 # GYP version: chrome/common/extensions/api/api.gyp:chrome_api
 json_schema_api("api") {
   schemas = true
   bundle = true
 
   deps = schema_dependencies
 }
 
 # GYP version: chrome/browser/extensions/api/api.gyp:chrome_api_registration
 json_schema_api("api_registration") {
   impl_dir = "//chrome/browser/extensions/api"
   bundle_registration = true
 
   deps = [
     # Different APIs include some headers from chrome/common that in turn
     # include generated headers from these targets.
     # TODO(brettw) this should be made unnecessary if possible.
     ":api",
+    "//components/copresence/proto",
     "//components/metrics/proto",
     "//skia",
     "//sync",
     "//ui/accessibility:ax_gen",
   ]
-  if (!is_ios && !is_android) {
-   deps += ["//components/copresence/proto"]
-  }
   if (is_chromeos) {
     # deps += [ "<(DEPTH)/chrome/chrome.gyp:drive_proto" ]  TODO(GYP)
   }
   deps += schema_dependencies
 }