[Feed] Add a feature flag for Feed notifications

This flag will be used to control whether to show notifications for
Feed articles.

Also, increase interest-feed-content-suggestions expiry milestone to 78.

Bug: 982483
Change-Id: I759721cd0e005612ecc40352f43e5608287591ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1693816
Commit-Queue: Ian Wells <[email protected]>
Reviewed-by: Dan H <[email protected]>
Reviewed-by: Sky Malice <[email protected]>
Cr-Commit-Position: refs/heads/master@{#677057}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 4837807..0f93ce9 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2121,6 +2121,10 @@
      FEATURE_WITH_PARAMS_VALUE_TYPE(feed::kInterestFeedContentSuggestions,
                                     kInterestFeedFeatureVariations,
                                     "InterestFeedContentSuggestions")},
+    {"interest-feed-notifications",
+     flag_descriptions::kInterestFeedNotificationsName,
+     flag_descriptions::kInterestFeedNotificationsDescription, kOsAndroid,
+     FEATURE_VALUE_TYPE(feed::kInterestFeedNotifications)},
     {"enable-ntp-remote-suggestions",
      flag_descriptions::kEnableNtpRemoteSuggestionsName,
      flag_descriptions::kEnableNtpRemoteSuggestionsDescription, kOsAndroid,