mash: Port TrayUpdateTest to AshTest

ash/common/wm_shell.h

Index: ash/common/wm_shell.h
diff --git a/ash/common/wm_shell.h b/ash/common/wm_shell.h
index 9e42f2f7e7e85fc3842fb0fb153012c7ecf73e36..ceb683eabb04097142e696547346958a3f68e52f 100644
--- a/ash/common/wm_shell.h
+++ b/ash/common/wm_shell.h
@@ -85,6 +85,10 @@ class WorkspaceEventHandler;
 enum class LoginStatus;
 enum class TaskSwitchSource;
 
+namespace mus {
+class WmTestHelper;
+}
+
 namespace wm {
 class MaximizeModeEventHandler;
 class WindowState;
@@ -457,6 +461,7 @@ class ASH_EXPORT WmShell {
   friend class AcceleratorControllerTest;
   friend class ScopedRootWindowForNewWindows;
   friend class Shell;
+  friend class mus::WmTestHelper;

[James Cook, 2016/10/11 19:58:37]

Lemme know if you would prefer a WmShellTestApi class.

[sky, 2016/10/11 20:56:24]

I think that would be cleaner, but if you want to do it separately I'm fine with
that.

 
   static WmShell* instance_;