gn: Remove unnecessary v8 defaults

chromecast/BUILD.gn

 # Copyright 2015 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/buildflag_header.gni")
 import("//build/config/features.gni")
 import("//build/config/locales.gni")
 import("//build/config/ui.gni")
-import("//build_overrides/v8.gni")
 import("//chromecast/build/tests/cast_test.gni")
 import("//chromecast/chromecast.gni")
 import("//media/media_options.gni")
 import("//tools/grit/repack.gni")
 import("//ui/ozone/ozone.gni")
+import("//v8/gni/v8.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 config("playready_config") {
   if (use_playready) {
     defines = [ "PLAYREADY_CDM_AVAILABLE" ]
   }
 }
@@ skipping 302 matching lines @@
     apk_name = "CastShell"
     android_manifest = "$root_gen_dir/cast_shell_manifest/AndroidManifest.xml"
     android_manifest_dep = "//chromecast/browser/android:cast_shell_manifest"
     deps = [
       ":cast_shell_apk_assets",
       "//chromecast/android:libcast_shell_android",
       "//chromecast/browser/android:cast_shell_java",
     ]
   }
 }