Enable external V8 snapshot on Android through GN.

build/config/features.gni

 # 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.
 
 # This file contains UI-related build flags. It should theoretically be in the
 # src/ui directory and only things that depend on the ui module should get the
 # definitions.
 #
 # However, today we have many "bad" dependencies on some of these flags from,
 # e.g. base, so they need to be global.
@@ skipping 139 matching lines @@
 # ChromeVox, which can then be enabled via a command-line switch.
 enable_chromevox_next = false
 
 # Use brlapi from brltty for braille display support.
 use_brlapi = is_chromeos
 
 # Option controlling the use of GConf (the classic GNOME configuration
 # system).
 # TODO(GYP) also require !embedded to enable.
 use_gconf = is_linux && !is_chromeos
+
+# TODO(baixo) enable this once this lands:
+# https://codereview.chromium.org/749213004
+# v8_use_external_startup_data = is_android && !is_android_webview_build
+v8_use_external_startup_data = false

[brettw, 2014/11/25 18:50:26]

I don't think this should be in "features.gni". I tried to express this in some
thread, but there were several threads and maybe not everybody was on all of
them.

The .gni files in this directory are basically all hacks that should go away.
Chrome feature flags shouldn't be in the build directory since the build
directory should be shared. But the current build expects everything to be
global, so I isolated the chrome flags into a couple of files here. The right
thing long-term to do is to have the ui flags in src/ui, the crypto flags in
src/crypto, etc.

For these flags that need to be set "on" v8 by different modules, I want to make
a new place for them (this thread you weren't on, sorry). My current favorite
name is "//build/module_args/v8.gni".

The idea is that it should be outside of "//build/config" since build/config is
the thing that should be shared between projects. For this new directory, each
project would have their own files that declare certain arguments for each
module they DEPS in. I put the name "module" in there because I want to
discourage people from dumping all build flags in there. These would only be the
ones that are exposed externally by a module.