Move ENABLE_PEPPER_CDMS to a buildflag header.

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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/features.gni")
 import("//chrome/process_version_rc_template.gni")
 import("//media/cdm/ppapi/cdm_paths.gni")
 import("//media/cdm/ppapi/ppapi_cdm_adapter.gni")
+import("//ppapi/features/features.gni")
 import("//third_party/widevine/cdm/widevine.gni")
 
 widevine_arch = current_cpu
 if (widevine_arch == "x86") {
   widevine_arch = "ia32"
 }
 
 widevine_cdm_binary_files = []
 widevine_cdm_manifest_file = []
 
@@ skipping 25 matching lines @@
   }
 } else if (enable_widevine) {
   widevine_cdm_version_h_file = "stub/widevine_cdm_version.h"
   widevine_cdm_manifest_file = [ "stub/manifest.json" ]
 } else {
   # No branding, use the default one.
   widevine_cdm_version_h_file = "widevine_cdm_version.h"
 }
 
 copy("version_h") {
+  visibility = [ ":*" ]  # Depend on ":headers" instead.
   sources = [
     widevine_cdm_version_h_file,
   ]
 
   # TODO(brettw) this should go into target_out_dir and callers should include
   # it from there. This requires, however, renaming the default
   # widevine_cdm_version.h in this directory to avoid conflicts.
   outputs = [
     "$root_gen_dir/widevine_cdm_version.h",
   ]
 }
 
+source_set("headers") {
+  public = [
+    "widevine_cdm_common.h",
+  ]
+
+  public_deps = [
+    ":version_h",  # Forward permission to use version header.
+    "//ppapi/features",
+  ]
+}
+
 if (widevine_cdm_binary_files != []) {
   copy("widevinecdm") {
     sources = widevine_cdm_binary_files
     outputs = [
       "$root_out_dir/$widevine_cdm_path/{{source_file_part}}",
     ]
 
     # TODO(jrummell)
     # 'COPY_PHASE_STRIP': 'NO',
   }
@@ skipping 94 matching lines @@
 # on the license server.
 source_set("widevine_test_license_server") {
   if (is_chrome_branded && is_linux) {
     deps = [
       # TODO(jrummell)
       # This target should be removed and targets should have data_deps on this target:
       #"//third_party/widevine/test/license_server/license_server.gyp:test_license_server"
     ]
   }
 }