media: Add External Clear Key content browser test on Android

components/cdm/renderer/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.
 
 static_library("renderer") {
   sources = [
+    "external_clear_key_key_system_properties.cc",
+    "external_clear_key_key_system_properties.h",
     "widevine_key_system_properties.cc",
     "widevine_key_system_properties.h",
   ]
 
   if (is_android) {
     sources += [
       "android_key_systems.cc",
       "android_key_systems.h",
     ]
   }
 
   deps = [
     "//base",
     "//components/cdm/common",
     "//content/public/renderer",
     "//media",
     "//third_party/widevine/cdm:version_h",
   ]
 }