[Media Router] Remove duplicate entries in BUILD

chrome/common/media_router/BUILD.gn

 # Copyright 2017 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("router") {
   public_deps = [
     "mojo:media_controller",
     "//base:base",
     "//base:i18n",
     "//net:net",
@@ skipping 19 matching lines @@
     "route_message.cc",
     "route_message.h",
     "route_request_result.cc",
     "route_request_result.h",
   ]
 
   if (!is_android) {
     public_deps += [ "mojo:media_router" ]
   }
 }
-
-source_set("unit_tests") {
-  testonly = true
-  public_deps = [
-    ":router",
-    "//base/test:test_support",
-    "//testing/gmock",
-    "//testing/gtest",
-    "//third_party/icu",
-  ]
-
-  sources = [
-    "discovery/media_sink_internal_unittest.cc",
-    "issue_unittest.cc",
-    "media_route_unittest.cc",
-    "media_sink_unittest.cc",
-    "media_source_helper_unittest.cc",
-    "media_source_unittest.cc",
-  ]
-
-  if (!is_android) {
-    public_deps += [ "mojo:media_router_test_interfaces" ]
-    sources += [ "mojo/media_router_struct_traits_unittest.cc" ]
-  }
-}