Make enable_service_discovery a chrome/ feature.

TBR=dbeam@chromium.org

Review-Url: https://codereview.chromium.org/2407483002
Cr-Original-Commit-Position: refs/heads/master@{#424019}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 4888f2982142523a4a0ddacfbf729f8d23a11e98
diff --git a/tools/gn/docs/cookbook.md b/tools/gn/docs/cookbook.md
index 0065b99..623f84f 100644
--- a/tools/gn/docs/cookbook.md
+++ b/tools/gn/docs/cookbook.md
@@ -259,7 +259,6 @@
 | `enable_basic_printing` (0/1)           | `enable_basic_printing` (true/false)           | `//build/config/features.gni` |
 | `enable_print_preview` (0/1)            | `enable_print_preview` (true/false)            | `//build/config/features.gni` |
 | `enable_rlz` (0/1)                      | `enable_rlz` (true/false)                      | `//build/config/features.gni` |
-| `enable_service_discovery` (0/1)        | `enable_service_discovery` (true/false)        | `//build/config/features.gni` |
 | `enable_spellcheck` (0/1)               | `enable_spellcheck` (true/false)               | `//build/config/features.gni` |
 | `enable_session_service` (0/1)          | `enable_session_service` (true/false)          | `//build/config/features.gni` |
 | `enable_task_manager` (0/1)             | `enable_task_manager` (true/false)             | `//build/config/features.gni` |