New Tab Page: add realbox "zero suggest" feature and update about:flags

Adds:
* kNtpZeroSuggest feature
* both kNtpRealbox and kNtpZeroSuggest to about:flags
* IsNtpRealboxEnabled() accessor, as zero suggest forces on realbox

[email protected]

Bug: 243926, 778489, 996516
Change-Id: Ifa91141c6459376a0e677b5c6ea527c13c5b59d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1769595
Auto-Submit: Dan Beam <[email protected]>
Reviewed-by: Moe Ahmadi <[email protected]>
Commit-Queue: Dan Beam <[email protected]>
Cr-Commit-Position: refs/heads/master@{#691015}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index 8efed91..c5c60683 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2776,11 +2776,23 @@
 const char kNtpCustomizationMenuV2Description[] =
     "Use the second version of the NTP customization menu.";
 
-extern const char kNtpDisableInitialMostVisitedFadeInName[] =
+const char kNtpDisableInitialMostVisitedFadeInName[] =
     "Disable NTP initial most visited fade in";
-extern const char kNtpDisableInitialMostVisitedFadeInDescription[] =
+const char kNtpDisableInitialMostVisitedFadeInDescription[] =
     "Do now initially fade in most visited tiles on the New Tab Page";
 
+const char kNtpRealboxName[] = "Real search box in New Tab Page";
+const char kNtpRealboxDescription[] =
+    "Enables a search box in the middle of the NTP that will accept input "
+    "directly (i.e. not be a \"fake\" box). Search results will show below the "
+    "non-fake input (\"realbox\").";
+
+const char kNtpZeroSuggestName[] =
+    "Suggest New Tab Page search results without input";
+const char kNtpZeroSuggestDescription[] =
+    "If enabled, forces on \"Real search box in New Tab Page\" and suggests "
+    "results without any typed input (i.e. on focus).";
+
 const char kEnableReaderModeName[] = "Enable Reader Mode";
 const char kEnableReaderModeDescription[] =
     "Allows viewing of simplified web pages by selecting 'Customize and "