[NTP::PhysicalWeb] Implement suggestion dismissal.

components/ntp_snippets/pref_names.h

Index: components/ntp_snippets/pref_names.h
diff --git a/components/ntp_snippets/pref_names.h b/components/ntp_snippets/pref_names.h
index a1f7dd1fc9f98bed3e99981bf5af4b46cf971935..c0ddda05cd0eaab5604cf7e4034a803197cda1af 100644
--- a/components/ntp_snippets/pref_names.h
+++ b/components/ntp_snippets/pref_names.h
@@ -44,9 +44,11 @@ extern const char kSnippetThumbnailsRequestsDay[];
 extern const char kLastSuccessfulBackgroundFetchTime[];
 
 extern const char kDismissedAssetDownloadSuggestions[];
-extern const char kDismissedRecentOfflineTabSuggestions[];
-extern const char kDismissedOfflinePageDownloadSuggestions[];
 extern const char kDismissedForeignSessionsSuggestions[];
+extern const char kDismissedOfflinePageDownloadSuggestions[];
+extern const char kDismissedPhysicalWebPageSuggestions[];
+extern const char kDismissedRecentOfflineTabSuggestions[];
+
 extern const char kDismissedCategories[];
 
 // The pref name for the discounted average number of browsing sessions per hour