mus: Use TooltipManagerAura in NativeWidgetMus.

ui/views/mus/screen_mus.cc

Index: ui/views/mus/screen_mus.cc
diff --git a/ui/views/mus/screen_mus.cc b/ui/views/mus/screen_mus.cc
index 84cf5b4dd8b015a1815177116048be224510098e..c3701c40ecbf3179cebcfac687923912a055ea08 100644
--- a/ui/views/mus/screen_mus.cc
+++ b/ui/views/mus/screen_mus.cc
@@ -11,6 +11,7 @@
 #include "services/shell/public/cpp/connection.h"
 #include "services/shell/public/cpp/connector.h"
 #include "ui/aura/window.h"
+#include "ui/views/mus/native_widget_mus.h"
 #include "ui/views/mus/screen_mus_delegate.h"
 #include "ui/views/mus/window_manager_frame_values.h"
 
@@ -81,6 +82,18 @@ bool ScreenMus::IsWindowUnderCursor(gfx::NativeWindow window) {
          window->GetBoundsInScreen().Contains(GetCursorScreenPoint());
 }
 
+gfx::NativeWindow ScreenMus::GetWindowAtScreenPoint(const gfx::Point& point) {
+  aura::Window* aura_window = nullptr;
+  ui::Window* ui_window = delegate_->GetWindowAtScreenPoint(point);
+  if (ui_window) {
+    NativeWidgetMus* nw_mus = NativeWidgetMus::GetForWindow(ui_window);
+    if (nw_mus)
+      aura_window =
+          static_cast<internal::NativeWidgetPrivate*>(nw_mus)->GetNativeView();

[Elliot Glaysher, 2016/10/04 22:27:19]

AFAICT based on the windows implementation of GetWindowAtScreenPoint, we
*aren't* supposed to recurse into |aura_window|. This method is supposed to
return the toplevel content window associated with the native widget.

+  }
+  return aura_window;
+}
+
 void ScreenMus::OnDisplays(mojo::Array<ui::mojom::WsDisplayPtr> ws_displays) {
   // This should only be called once from Init() before any observers have been
   // added.