Add experiment flag for hiding articles on NTP

Bug: 803525
Change-Id: Ie97cf5306fbad1f095306651a4680e5718d3088c
Reviewed-on: https://chromium-review.googlesource.com/896393
Reviewed-by: Theresa <[email protected]>
Reviewed-by: Bernhard Bauer <[email protected]>
Commit-Queue: Becky Zhou <[email protected]>
Cr-Commit-Position: refs/heads/master@{#533685}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 3045934..7df8b49 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -1911,6 +1911,12 @@
 const char kEnableExpandedAutofillCreditCardPopupLayoutDescription[] =
     "If enabled, displays autofill credit card popup using expanded layout.";
 
+const char kEnableNtpArticleSuggestionsExpandableHeaderName[] =
+    "Show article suggestions expandable header on New Tab Page";
+const char kEnableNtpArticleSuggestionsExpandableHeaderDescription[] =
+    "If enabled, the article suggestions content on New Tab Page can be "
+    "toggled shown or hidden by clicking the expandable header.";
+
 const char kEnableNtpAssetDownloadSuggestionsName[] =
     "Show asset downloads on the New Tab page";
 const char kEnableNtpAssetDownloadSuggestionsDescription[] =