[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 d474d4c482cca5df4810bc6c246b72d5c99da12e..24be7be6d56213a90c222c5c1d56e41b944935bf 100644
--- a/components/ntp_snippets/pref_names.h
+++ b/components/ntp_snippets/pref_names.h
@@ -41,9 +41,11 @@ extern const char kSnippetThumbnailsInteractiveRequestCount[];
 extern const char kSnippetThumbnailsRequestsDay[];
 
 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