Implement ClearHistory for all ntp_snippets providers

components/ntp_snippets/bookmarks/bookmark_last_visit_utils.cc

Index: components/ntp_snippets/bookmarks/bookmark_last_visit_utils.cc
diff --git a/components/ntp_snippets/bookmarks/bookmark_last_visit_utils.cc b/components/ntp_snippets/bookmarks/bookmark_last_visit_utils.cc
index ed94a9bb493cd793af6e5e79b0368e0174dfd657..05a7fa2f3350ff0b8a25d98c6fe815f0e65b3930 100644
--- a/components/ntp_snippets/bookmarks/bookmark_last_visit_utils.cc
+++ b/components/ntp_snippets/bookmarks/bookmark_last_visit_utils.cc
@@ -232,4 +232,21 @@ std::vector<const BookmarkNode*> GetDismissedBookmarksForDebugging(
   return result;
 }
 
+void RemoveAllLastVisitDates(bookmarks::BookmarkModel* bookmark_model) {
+  // Get all the bookmark URLs.
+  std::vector<BookmarkModel::URLAndTitle> bookmark_urls;
+  bookmark_model->GetBookmarks(&bookmark_urls);
+
+  for (const BookmarkModel::URLAndTitle& url_and_title : bookmark_urls) {
+    // Get all bookmarks for the given URL.
+    std::vector<const BookmarkNode*> bookmarks_for_url;
+    bookmark_model->GetNodesByURL(url_and_title.url, &bookmarks_for_url);
+    DCHECK(!bookmarks_for_url.empty());

[Marc Treib, 2016/09/01 14:11:20]

No need to check for this - it shouldn't happen, but also nothing bad will
happen here if it did, so.. eh.

[vitaliii, 2016/09/01 14:45:15]

Done.

+
+    for (const BookmarkNode* bookmark : bookmarks_for_url) {
+      bookmark_model->DeleteNodeMetaInfo(bookmark, kBookmarkLastVisitDateKey);
+    }
+  }
+}
+
 }  // namespace ntp_snippets