MD History: Add title to item menu button

This matches the behavior of the existing history page.

BUG=623014
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2106363002
Cr-Commit-Position: refs/heads/master@{#403387}

chrome/browser/resources/md_history/history_item.html

@@ -145,7 +145,7 @@
         </div>
         <iron-icon icon="cr:star" id="bookmark-star"></iron-icon>
         <button is="paper-icon-button-light" id="menu-button"
-            on-tap="onMenuButtonTap_">
+            on-tap="onMenuButtonTap_" title="$i18n{moreActionsButton}">
           <iron-icon icon="cr:more-vert"></iron-icon>
         </button>
       </div>

chrome/browser/ui/webui/md_history_ui.cc

@@ -50,6 +50,8 @@ content::WebUIDataSource* CreateMdHistoryUIHTMLSource(Profile* profile) {
                              IDS_MD_HISTORY_HISTORY_MENU_ITEM);
   source->AddLocalizedString("itemsSelected", IDS_MD_HISTORY_ITEMS_SELECTED);
   source->AddLocalizedString("loading", IDS_HISTORY_LOADING);
+  source->AddLocalizedString("moreActionsButton",
+                             IDS_HISTORY_ACTION_MENU_DESCRIPTION);
   source->AddLocalizedString("moreFromSite", IDS_HISTORY_MORE_FROM_SITE);
   source->AddLocalizedString("openAll", IDS_HISTORY_OTHER_SESSIONS_OPEN_ALL);
   source->AddLocalizedString("openTabsMenuItem",