MD History: promote menu button to show clear browsing data in narrow mode

chrome/browser/ui/webui/md_history_ui.h

Index: chrome/browser/ui/webui/md_history_ui.h
diff --git a/chrome/browser/ui/webui/md_history_ui.h b/chrome/browser/ui/webui/md_history_ui.h
index 117aff21c230464c2c3cb612240e631a0c3feead..f75b7be7f227530bd0e311612e44339acfb0a612 100644
--- a/chrome/browser/ui/webui/md_history_ui.h
+++ b/chrome/browser/ui/webui/md_history_ui.h
@@ -12,9 +12,18 @@
 class Profile;
 
 namespace base {
+class ListValue;
 class RefCountedMemory;
 }
 
+namespace content {
+class WebUIDataSource;
+}
+
+namespace user_prefs {
+class PrefRegistrySyncable;
+}
+
 class MdHistoryUI : public content::WebUIController {
  public:
   explicit MdHistoryUI(content::WebUI* web_ui);
@@ -24,10 +33,17 @@ class MdHistoryUI : public content::WebUIController {
   // Reset the current list of features and explicitly disable MD History.
   static void DisableForTesting();
 
+  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
+
   static base::RefCountedMemory* GetFaviconResourceBytes(
       ui::ScaleFactor scale_factor);
 
  private:
+  // Handler for the "menuPromoShown" message from the page. No arguments.
+  void HandleMenuPromoShown(const base::ListValue* args);
+
+  content::WebUIDataSource* data_source_;  // weak
+
   DISALLOW_COPY_AND_ASSIGN(MdHistoryUI);
 };