mash: Add touch-hud app.

ash/mus/root_window_controller.cc

Index: ash/mus/root_window_controller.cc
diff --git a/ash/mus/root_window_controller.cc b/ash/mus/root_window_controller.cc
index 3a3f0d17551dd066b1f005012b5c71e60fe2d8f4..49dd56e4a4eeb89010c2100212ca4a04e87f4bb4 100644
--- a/ash/mus/root_window_controller.cc
+++ b/ash/mus/root_window_controller.cc
@@ -180,6 +180,14 @@ gfx::Rect RootWindowController::CalculateDefaultBounds(
         ::ui::mojom::WindowManager::kInitialBounds_Property);
   }
 
+  if (window->HasSharedProperty(
+          ::ui::mojom::WindowManager::kShowState_Property) &&
+      static_cast<::ui::mojom::ShowState>(window->GetSharedProperty<int32_t>(
+          ::ui::mojom::WindowManager::kShowState_Property)) ==
+          ui::mojom::ShowState::FULLSCREEN) {
+    return gfx::Rect(0, 0, root_->bounds().width(), root_->bounds().height());
+  }
+
   int width, height;
   const gfx::Size pref = GetWindowPreferredSize(window);
   if (pref.IsEmpty()) {