Move ENABLE_PEPPER_CDMS to a buildflag header.

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.
 
 # =============================================
 #   PLEASE DO NOT ADD MORE FLAGS TO THIS FILE
 # =============================================
 #
 # These flags are effectively global. Your feature flag should go near the
 # code it controls. Most of these items are here now because they control
@@ skipping 115 matching lines @@
 
 # Enable the spell checker.
 enable_spellcheck = !is_ios
 
 # Use the operating system's spellchecker rather than hunspell.
 use_browser_spellchecker = is_android || is_mac
 
 # Use Minikin hyphenation engine.
 use_minikin_hyphenation = is_android
 
-# Enables the use of CDMs in pepper plugins.
-enable_pepper_cdms =
-    enable_plugins && (is_linux || is_mac || is_win) && !is_chromecast
-
 # The seccomp-bpf sandbox is only supported on five architectures
 # currently.
 # Do not disable seccomp_bpf anywhere without talking to
 # security@chromium.org!
 use_seccomp_bpf =
     (is_linux || is_android) &&
     (current_cpu == "x86" || current_cpu == "x64" || current_cpu == "arm" ||
      current_cpu == "arm64" || current_cpu == "mipsel")
 
 # Enable notifications everywhere except iOS.
@@ skipping 22 matching lines @@
 
 enable_configuration_policy = !is_ios
 
 enable_mac_keystone = is_mac && is_chrome_branded && is_official_build
 #
 # =============================================
 #   PLEASE DO NOT ADD MORE FLAGS TO THIS FILE
 # =============================================
 #
 # See comment at the top.