Move some global feature defines to buildflags

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 9d9571563d2bca9469a57aa9c47785938acbcae0..fd34e1829b9b758800fb02507af1926a108cec73 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -196,18 +196,12 @@ config("feature_flags") {
   if (enable_themes) {
     defines += [ "ENABLE_THEMES=1" ]
   }
-  if (enable_captive_portal_detection) {
-    defines += [ "ENABLE_CAPTIVE_PORTAL_DETECTION=1" ]
-  }
   if (enable_session_service) {
     defines += [ "ENABLE_SESSION_SERVICE=1" ]
   }
   if (enable_rlz) {
     defines += [ "ENABLE_RLZ" ]
   }
-  if (enable_plugin_installation) {
-    defines += [ "ENABLE_PLUGIN_INSTALLATION=1" ]
-  }
   if (enable_app_list) {
     defines += [ "ENABLE_APP_LIST=1" ]
   }
@@ -226,9 +220,6 @@ config("feature_flags") {
   if (proprietary_codecs) {
     defines += [ "USE_PROPRIETARY_CODECS" ]
   }
-  if (enable_hangout_services_extension) {
-    defines += [ "ENABLE_HANGOUT_SERVICES_EXTENSION=1" ]
-  }
   if (safe_browsing_mode == 1) {
     defines += [ "FULL_SAFE_BROWSING" ]
     defines += [ "SAFE_BROWSING_CSD" ]