aura: Allow specifying the size of TestScreen when creating it.

apps/shell/browser/shell_desktop_controller.cc

Index: apps/shell/browser/shell_desktop_controller.cc
diff --git a/apps/shell/browser/shell_desktop_controller.cc b/apps/shell/browser/shell_desktop_controller.cc
index 2db85b792b12225ceeab2e7037ebd9fe48b382b2..5c90db0ca7da37c790725a02b860c6d50ab5b418 100644
--- a/apps/shell/browser/shell_desktop_controller.cc
+++ b/apps/shell/browser/shell_desktop_controller.cc
@@ -224,16 +224,16 @@ void ShellDesktopController::OnHostCloseRequested(
 }
 
 void ShellDesktopController::CreateRootWindow() {
-  test_screen_.reset(aura::TestScreen::Create());
-  // TODO(jamescook): Replace this with a real Screen implementation.
-  gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, test_screen_.get());
-  // TODO(mukai): Set up input method.
-
   // Set up basic pieces of ui::wm.
   gfx::Size size = GetPrimaryDisplaySize();
   if (size.IsEmpty())
     size = gfx::Size(1366, 768);
 
+  test_screen_.reset(aura::TestScreen::Create(size));
+  // TODO(jamescook): Replace this with a real Screen implementation.
+  gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, test_screen_.get());
+  // TODO(mukai): Set up input method.
+
   host_.reset(aura::WindowTreeHost::Create(gfx::Rect(size)));
   host_->InitHost();
   aura::client::SetWindowTreeClient(host_->window(), this);