Revert "chromeos: gets more ash_unittests working with single-process mash"

This reverts commit 41b5497b.

Reason for revert: Caused ash_content_unittests failure on linux-chromeos-dbg - https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-dbg/7312

Original change's description:
> chromeos: gets more ash_unittests working with single-process mash
> 
> The OverviewButtonTrayTests need to set the keyboard devices *after*
> AshTestBase::SetUp() is called. This is is important in single-process mash
> as Ash is the one creating the Env that the keyboard devices us. In
> non-single-process-mash AshTestSuite is creating the Env these tests use.
> 
> The case ShellTest2.DontCrashWhenWindowDeleted is exercising is different
> enough for single-process mash that I created a separate test.
> 
> Adding NOPRESUBMIT=true as this bot passed the trybots, and we're ok with
> this test including Env::GetInstance().
> 
> NOPRESUBMIT=true
> 
> BUG=847992
> TEST=test only changes
> 
> Change-Id: I0543db96ca9aa910340360d8da3e6aafcda34d7f
> Reviewed-on: https://chromium-review.googlesource.com/1174978
> Commit-Queue: Scott Violet <sky@chromium.org>
> Reviewed-by: James Cook <jamescook@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#583161}

TBR=jamescook@chromium.org,sky@chromium.org

Change-Id: Ib23d73ef909ac7fe2c9821d7ca8203228bd7fb4a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 847992
Reviewed-on: https://chromium-review.googlesource.com/1174493Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583197}

ash/shell_unittest.cc

@@ -34,12 +34,9 @@
 #include "components/prefs/testing_pref_service.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/env.h"
-#include "ui/aura/test/mus/test_window_tree_client_delegate.h"
-#include "ui/aura/test/mus/test_window_tree_client_setup.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/models/simple_menu_model.h"
-#include "ui/base/ui_base_features.h"
 #include "ui/events/test/event_generator.h"
 #include "ui/events/test/events_test_utils.h"
 #include "ui/events/test/test_event_handler.h"
@@ -589,59 +586,6 @@ class ShellTest2 : public AshTestBase {
 };
 
 TEST_F(ShellTest2, DontCrashWhenWindowDeleted) {
-  // DontCrashWhenWindowDeletedSingleProcess covers the SingleProcessMash case.
-  if (::features::IsSingleProcessMash())
-    return;
-
-  window_ = std::make_unique<aura::Window>(nullptr,
-                                           aura::client::WINDOW_TYPE_UNKNOWN);
-  window_->Init(ui::LAYER_NOT_DRAWN);
-}
-
-// This verifies WindowObservers are removed when a window is destroyed after
-// the Shell is destroyed. This scenario (aura::Windows being deleted after the
-// Shell) occurs if someone is holding a reference to an unparented Window, as
-// is the case with a RenderWidgetHostViewAura that isn't on screen. As long as
-// everything is ok, we won't crash. If there is a bug, window's destructor will
-// notify some deleted object (say VideoDetector or ActivationController) and
-// this will crash.
-class ShellTest3 : public AshTestBase {
- public:
-  ShellTest3() = default;
-  ~ShellTest3() override = default;
-
-  void SetUp() override {
-    AshTestBase::SetUp();
-    if (!::features::IsSingleProcessMash())
-      return;
-    window_service_setup_ = std::make_unique<aura::TestWindowTreeClientSetup>();
-    window_service_setup_->InitWithoutEmbed(&test_window_tree_client_delegate_);
-    aura::Env::GetInstance()->SetWindowTreeClient(
-        window_service_setup_->window_tree_client());
-  }
-
-  void TearDown() override {
-    AshTestBase::TearDown();
-    if (!::features::IsSingleProcessMash())
-      return;
-    window_.reset();
-    window_service_setup_.reset();
-    aura::Env::GetInstance()->SetWindowTreeClient(nullptr);
-  }
-
- protected:
-  std::unique_ptr<aura::Window> window_;
-
- private:
-  aura::TestWindowTreeClientDelegate test_window_tree_client_delegate_;
-  std::unique_ptr<aura::TestWindowTreeClientSetup> window_service_setup_;
-
-  DISALLOW_COPY_AND_ASSIGN(ShellTest3);
-};
-
-TEST_F(ShellTest3, DontCrashWhenWindowDeletedSingleProcess) {
-  if (!::features::IsSingleProcessMash())
-    return;
   // This test explicitly uses aura::Env::GetInstance() rather than
   // Shell->aura_env() as the Window outlives the Shell. In order for a Window
   // to outlive Shell the Window must be created outside of Ash, which uses

ash/system/overview/overview_button_tray_unittest.cc

@@ -77,11 +77,11 @@ class OverviewButtonTrayTest : public AshTestBase {
     base::CommandLine::ForCurrentProcess()->AppendSwitch(
         ::switches::kUseFirstDisplayAsInternal);
 
-    AshTestBase::SetUp();
-
     ui::InputDeviceClientTestApi().SetKeyboardDevices({ui::InputDevice(
         3, ui::InputDeviceType::INPUT_DEVICE_INTERNAL, "keyboard")});
     base::RunLoop().RunUntilIdle();
+
+    AshTestBase::SetUp();
   }
 
   // Enters or exits tablet mode. Use these instead of