Use mojo SystemTray interfaces for both mash and classic ash

ash/common/shell_delegate.h

Index: ash/common/shell_delegate.h
diff --git a/ash/common/shell_delegate.h b/ash/common/shell_delegate.h
index 316cd5345d6ff6f06a8a48d18963a267d5db5910..f0d61707f2ec9d927f0c47c50369e6cff4b080e0 100644
--- a/ash/common/shell_delegate.h
+++ b/ash/common/shell_delegate.h
@@ -31,6 +31,10 @@ namespace ui {
 class MenuModel;
 }
 
+namespace shell {
+class Connector;
+}
+
 namespace views {
 class Widget;
 }
@@ -57,6 +61,9 @@ class ASH_EXPORT ShellDelegate {
   // The Shell owns the delegate.
   virtual ~ShellDelegate() {}
 
+  // Returns the connector for the mojo service manager. Returns null in tests.
+  virtual ::shell::Connector* GetShellConnector() const = 0;
+
   // Returns true if this is the first time that the shell has been run after
   // the system has booted.  false is returned after the shell has been
   // restarted, typically due to logging in as a guest or logging out.