Convert RLZ to a buildflag header

Creates a new directory rlz/features for the gni file and the buildflag_header target.

Updates callers to depend on the new target and use the new flags.

Review-Url: https://codereview.chromium.org/2570573002
Cr-Original-Commit-Position: refs/heads/master@{#438026}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8fb852d9e627bd3d1042700072e98d2884d48933

config/BUILD.gn

@@ -136,9 +136,6 @@ config("feature_flags") {
   if (!enable_nacl) {
     defines += [ "DISABLE_NACL" ]
   }
-  if (enable_rlz) {
-    defines += [ "ENABLE_RLZ" ]
-  }
   if (enable_wayland_server) {
     defines += [ "ENABLE_WAYLAND_SERVER=1" ]
   }

config/features.gni

@@ -79,11 +79,6 @@ declare_args() {
 
 # Additional dependent variables -----------------------------------------------
 
-# Whether we are using the rlz library or not.  Platforms like Android send
-# rlz codes for searches but do not use the library.
-enable_rlz_support = is_win || is_mac || is_ios || is_chromeos
-enable_rlz = is_chrome_branded && enable_rlz_support
-
 # Chrome OS: whether to also build the upcoming version of
 # ChromeVox, which can then be enabled via a command-line switch.
 enable_chromevox_next = false