Add a policy to allow NTP promotions & default apps to be disabled.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 126d0cec8e9d76d39f0fe21d3d14407189645389..c676ca29d69de4d3e3815084388880777ea64a7d 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1212,6 +1212,9 @@ const char kNTPWebStorePromoUserGroup[] = "ntp.webstorepromo.usergroup";
 // Customized app page names that appear on the New Tab Page.
 const char kNTPAppPageNames[] = "ntp.app_page_names";
 
+// When true, web store promos will never be shown.
+const char kNTPHideWebStorePromo[] = "ntp.hide_webstore_promo";
+
 // The most up-to-date GPU blacklist downloaded from the web, which replaces
 // the one that's installed with chrome.
 const char kGpuBlacklist[] = "gpu_blacklist";