[Chrome OS MD] Implement accessibility detailed view for the MD Ash system menu

ash/common/system/tray_accessibility.h

Index: ash/common/system/tray_accessibility.h
diff --git a/ash/common/system/tray_accessibility.h b/ash/common/system/tray_accessibility.h
index 1c280e317a957554a19e5b9348fcde0a22812e23..baa8143ff631465d81ba6a23237b69e9fcc605ec 100644
--- a/ash/common/system/tray_accessibility.h
+++ b/ash/common/system/tray_accessibility.h
@@ -66,9 +66,14 @@ class AccessibilityDetailedView : public TrayDetailsView,
   // Add help entries.
   void AppendHelpEntries();
 
+  // Helper functions to create entries in the detailed accessibility view.
   HoverHighlightView* AddScrollListItem(const base::string16& text,
                                         bool highlight,
                                         bool checked);
+  HoverHighlightView* AddScrollListItemMD(const base::string16& text,
+                                          bool highlight,
+                                          bool checked,
+                                          const gfx::ImageSkia& image);
 
   views::View* spoken_feedback_view_;
   views::View* high_contrast_view_;