Prevent deprecation of the enable-quic flag

Change-Id: I7533673833cae9e9356fd9b0589d8a8f9b2da0b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593388
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Auto-Submit: David Schinazi <dschinazi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#837601}

chrome/browser/flag-metadata.json

@@ -2108,7 +2108,9 @@
   {
     "name": "enable-quic",
     "owners": [ "//net/quic/OWNERS" ],
-    "expiry_milestone": 88
+    // This flag is used by network administrators to debug
+    // network issues related to QUIC. It must not be removed.
+    "expiry_milestone": -1
   },
   {
     "name": "enable-quick-answers",

chrome/browser/flag-never-expire-list.json

@@ -46,6 +46,7 @@
   "enable-noscript-previews",
   "enable-offline-previews",
   "enable-parallel-downloading",
+  "enable-quic",
   "enable-reader-mode-in-cct",
   "enable-resource-loading-hints",
   "enable-save-data",