Makes DefaultCaptureClient work with a null root_window

ui/aura/test/aura_test_helper.cc

 // Copyright (c) 2012 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.
 
 #include "ui/aura/test/aura_test_helper.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "ui/aura/client/default_capture_client.h"
 #include "ui/aura/client/focus_client.h"
@@ skipping 60 matching lines @@
   gfx::Size host_size(screen ? screen->GetPrimaryDisplay().GetSizeInPixel()
                              : gfx::Size(800, 600));
   test_screen_.reset(TestScreen::Create(host_size));
   if (!screen)
     display::Screen::SetScreenInstance(test_screen_.get());
   host_.reset(test_screen_->CreateHostForPrimaryDisplay());
 
   focus_client_.reset(new TestFocusClient);
   client::SetFocusClient(root_window(), focus_client_.get());
   parenting_client_.reset(new TestWindowParentingClient(root_window()));
-  capture_client_.reset(new client::DefaultCaptureClient(root_window()));
+  capture_client_ = base::MakeUnique<client::DefaultCaptureClient>();
+  SetCaptureClient(host_->window(), capture_client_.get());

[msw, 2016/10/25 19:21:08]

nit: client:: needed here like below?

[msw, 2016/10/25 19:21:08]

aside: odd that host_->window()'s root is not root_window()...
(I haven't looked closely to actually figure this out...)

[sky, 2016/10/25 19:44:40]

Surprisingly it isn't needed here, but is needed below. That is, this compiles,
but if I remove client:: from below I get:

../../ui/aura/test/aura_test_helper.cc:92:3: error: use of undeclared identifier
'SetCaptureClient'; did you mean 'client::SetCaptureClient'?
  SetCaptureClient(host_->window(), nullptr);
  ^~~~~~~~~~~~~~~~
  client::SetCaptureClient
../../ui/aura/client/capture_client.h:44:18: note: 'client

I stepped through this code to ensure it calls to aura::client::SetCaptureClient
and it does. I'm speculating, but I'm guessing having a type in capture_client_
makes this call work without the client:: where as the code below has no type,
so it fails.

[msw, 2016/10/25 19:47:59]

Odd... I might add it to be clear/consistent, but it's up to you.

 
   root_window()->Show();
   // Ensure width != height so tests won't confuse them.
   host()->SetBounds(gfx::Rect(host_size));
 }
 
 void AuraTestHelper::TearDown() {
   teardown_called_ = true;
   parenting_client_.reset();
+  client::SetCaptureClient(host_->window(), nullptr);
   capture_client_.reset();
   focus_client_.reset();
   client::SetFocusClient(root_window(), nullptr);
   host_.reset();
   ui::GestureRecognizer::Reset();
   if (display::Screen::GetScreen() == test_screen_.get())
     display::Screen::SetScreenInstance(nullptr);
   test_screen_.reset();
 
 #if defined(USE_X11)
   ui::test::ResetXCursorCache();
 #endif
 
   ui::ShutdownInputMethodForTesting();
 
   env_.reset();
 }
 
 void AuraTestHelper::RunAllPendingInMessageLoop() {
   // TODO(jbates) crbug.com/134753 Find quitters of this RunLoop and have them
   //              use run_loop.QuitClosure().
   base::RunLoop run_loop;
   run_loop.RunUntilIdle();
 }
 
 }  // namespace test
 }  // namespace aura