[webui][ntp] Extend several feature flags

Extend
- #ntp-iframe-one-google-bar
- #ntp-one-google-bar-modal-overlays
- #ntp-webui

Features still haven't fully launched yet and flags allow us to more
easily test in e.g. Chrome Canary.

Fixed: 1121060

Change-Id: I20987e07ff4469bb096db8b6a5d1390b05f99101
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2376308Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Auto-Submit: Tibor Goldschwendt <tiborg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801555}

chrome/browser/flag-metadata.json

@@ -3128,7 +3128,7 @@
   {
     "name": "ntp-iframe-one-google-bar",
     "owners": [ "aee", "mahmadi", "tiborg" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 87
   },
   {
     "name": "ntp-modules",
@@ -3138,7 +3138,7 @@
   {
     "name": "ntp-one-google-bar-modal-overlays",
     "owners": [ "aee", "mahmadi", "tiborg" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 87
   },
   {
     "name": "ntp-realbox",
@@ -3158,7 +3158,7 @@
   {
     "name": "ntp-webui",
     "owners": [ "aee", "mahmadi", "tiborg" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 87
   },
   {
     "name": "offline-indicator-always-http-probe",