Use mojo SystemTray interfaces for both mash and classic ash

ash/mus/window_manager.cc

Index: ash/mus/window_manager.cc
diff --git a/ash/mus/window_manager.cc b/ash/mus/window_manager.cc
index 87530fa822eda4f699fe8e5dad558d113eb2ac6c..bff7bb124e90312c3c8c9d801632e6a2b808131f 100644
--- a/ash/mus/window_manager.cc
+++ b/ash/mus/window_manager.cc
@@ -78,7 +78,7 @@ void WindowManager::Init(
 
   shell_.reset(new WmShellMus(base::MakeUnique<ShellDelegateMus>(connector_),

[msw, 2016/09/30 23:26:49]

q: Would it make sense for the shell delegate to provide an accessor to its
connector, since it's the owner? Then shell init can just access it that way.
It's no big deal either way, especially if that complicates ash::Shell init.

                               this, pointer_watcher_event_router_.get()));
-  shell_->Initialize(blocking_pool);
+  shell_->Initialize(blocking_pool, connector_);
   lookup_.reset(new WmLookupMus);
 }