chromeos: Makes AshTestBase/Helper target mash when appropriate

ash/mus/bridge/wm_shell_mus.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_MUS_BRIDGE_WM_SHELL_MUS_H_
 #define ASH_MUS_BRIDGE_WM_SHELL_MUS_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 18 matching lines @@
 
 class AcceleratorControllerDelegateMus;
 class AcceleratorControllerRegistrar;
 class ImmersiveHandlerFactoryMus;
 class WindowManager;
 class WmShellMusTestApi;
 
 // WmShell implementation for mus.
 class WmShellMus : public WmShell {
  public:
+  // If |create_session_state_delegate_stub| is true SessionStateDelegateStub is
+  // created. If false, the SessionStateDelegate from Shell is used.
   WmShellMus(WmWindow* primary_root_window,
              std::unique_ptr<ShellDelegate> shell_delegate,
              WindowManager* window_manager,
-             views::PointerWatcherEventRouter* pointer_watcher_event_router);
+             views::PointerWatcherEventRouter* pointer_watcher_event_router,
+             bool create_session_state_delegate_stub);

[msw, 2017/02/19 21:49:20]

Can we just rely on the shell_delegate for this?
ShellDelegateMus::CreateSessionStateDelegate already makes a stub.

[sky, 2017/02/21 17:06:50]

Shell::Init() creates a SessionStateDelegate:

  session_state_delegate_.reset(
      wm_shell_->delegate()->CreateSessionStateDelegate());

In test code this ends up in TestShellDelegate::CreateSessionStateDelegate(),
which creates a TestSessionStateDelegate. Test code depends upon
TestSessionStateDelegate:

// static
TestSessionStateDelegate* AshTestHelper::GetTestSessionStateDelegate() {
  CHECK(WmShell::HasInstance());
  return static_cast<TestSessionStateDelegate*>(
      WmShell::Get()->GetSessionStateDelegate());
}

In other words the test code wants to use TestSessionStateDelegate, which I made
it get by having WmShellMus not create a SessionStateDelegate so that in:

SessionStateDelegate* WmShellMus::GetSessionStateDelegate() {
  return session_state_delegate_
             ? session_state_delegate_.get()
             : Shell::GetInstance()->session_state_delegate();
}

WmShellMus::session_state_delegate_ is null, and the code falls back to that of
Shell, which is TestSessionStateDelegate.

It seems the right fix is that both Shell and WmShellMus shouldn't create
SessionStateDelegate, only Shell. That's a bigger change though.

[msw, 2017/02/22 06:25:48]

Got it, it'd be nice to summarize that in a bug or comment. It's slightly
confusing without that explainer.

   ~WmShellMus() override;
 
   static WmShellMus* Get();
 
   ash::RootWindowController* GetRootWindowControllerWithDisplayId(int64_t id);
 
   AcceleratorControllerDelegateMus* accelerator_controller_delegate() {
     return accelerator_controller_delegate_.get();
   }
 
@@ skipping 76 matching lines @@
   std::unique_ptr<ImmersiveHandlerFactoryMus> immersive_handler_factory_;
   std::unique_ptr<SessionStateDelegate> session_state_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(WmShellMus);
 };
 
 }  // namespace mus
 }  // namespace ash
 
 #endif  // ASH_MUS_BRIDGE_WM_SHELL_MUS_H_