Replace WIDEVINE_CDM_AVAILABLE with a gyp define 'enable_widevine_cdm'.

third_party/widevine/cdm/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.
 
 widevine_arch = cpu_arch
 if (widevine_arch == "x86") {
   widevine_arch = "ia32"
 }
 
-if (is_android) {
-  # Always available on Android regardless of branding.
-  widevine_cdm_version_h_file = "android/widevine_cdm_version.h"
-  widevine_cdm_binary_files = []
-} else if (is_chrome_branded) {
-  if (is_chromeos) {
+if (enable_widevine) {
+  if (is_android) {
+    widevine_cdm_version_h_file = "android/widevine_cdm_version.h"
+    widevine_cdm_binary_files = []
+  } else if (is_chromeos) {
     widevine_cdm_version_h_file =
       "chromeos/$widevine_arch/widevine_cdm_version.h"
     widevine_cdm_binary_files = [
       "chromeos/$widevine_arch/libwidevinecdm.so",
     ]
   } else if (is_linux) {
     widevine_cdm_version_h_file =
       "linux/$widevine_arch/widevine_cdm_version.h"
     widevine_cdm_binary_files = [
       "linux/$widevine_arch/libwidevinecdm.so",
@@ skipping 39 matching lines @@
 } else {
   copy("binaries") {
     sources = widevine_cdm_binary_files
     outputs = [ "$root_out_dir/{{source_file_part}}" ]
     # TODO(GYP)
     # 'COPY_PHASE_STRIP': 'NO',
   }
 }
 
 source_set("adapter") {
-  if (is_chrome_branded) {
+  if (enable_widevine) {
     deps = [
       ":version_h",
       ":binaries",
       "//ppapi:ppapi_cpp",
       #'<(DEPTH)/media/media_cdm_adapter.gyp:cdmadapter',  TODO(GYP)
     ]
   }
 
   if (is_linux) {
     libs = [ rebase_path("$root_out_dir/libwidevinecdm.so", root_build_dir)  ]
   } else if (is_win) {
     libs = [ rebase_path("$root_out_dir/widevinecdm.dll.lib", root_build_dir) ]
   } else if (is_mac) {
     libs = [ rebase_path("$root_out_dir/libwidevinecdm.dylib", root_build_dir) ]
   }
 }
 
 # This target exists for tests to depend on that pulls in a runtime dependency
 # on the license server.
 source_set("widevine_test_license_server") {
-  if (is_chrome_branded && is_linux) {
+  if (enable_widevine && is_linux) {
     deps = [
       # TODO(GYP)
       #"//third_party/widevine/test/license_server/license_server.gyp:test_license_server"
     ]
   }
 }