[ios] Enable AboutFlagsTest.EveryFlagHasMetadata

We're bringing Chrome Flag Ownership to iOS
go/chrome-flags-ios

More about flag ownership here:
https://chromium.googlesource.com/chromium/src/+/master/docs/flag_ownership.md

See announcement here:
https://groups.google.com/a/google.com/g/bling-team/c/7YC_3l6yEzo/m/1-iZg1fPAAAJ

This CL enables the unit test that enforces flag ownership in iOS.

Prior to this being enabled, all iOS flags in
//ios/chrome/browser/flags/about_flags.mm must have a corresponding
entry in flag-metadata.json.

Bug: 1058614
Change-Id: I6fb93f4f10503233caa0934331c2d25fdeaaaa50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095557Reviewed-by: Eugene But <eugenebut@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749387}

ios/chrome/browser/flags/about_flags_unittest.mm

@@ -16,9 +16,7 @@ using AboutFlagsTest = PlatformTest;
 
 // Makes sure that every flag has an owner and an expiry entry in
 // flag-metadata.json.
-// TODO(crbug.com/1058614): Enable once iOS flags are added to
-// flag-metadata.json.
-TEST_F(AboutFlagsTest, DISABLED_EveryFlagHasMetadata) {
+TEST_F(AboutFlagsTest, EveryFlagHasMetadata) {
   size_t count;
   const flags_ui::FeatureEntry* entries = testing::GetFeatureEntries(&count);
   flags_ui::testing::EnsureEveryFlagHasMetadata(entries, count);