Adds additional_client_area to client area

ui/aura/mus/window_tree_host_mus.cc

Index: ui/aura/mus/window_tree_host_mus.cc
diff --git a/ui/aura/mus/window_tree_host_mus.cc b/ui/aura/mus/window_tree_host_mus.cc
index 895ef4b7f47f9ec1c93a32d84484f193f74c9040..c5c314b025a28991f753584410aefd0d430d1126 100644
--- a/ui/aura/mus/window_tree_host_mus.cc
+++ b/ui/aura/mus/window_tree_host_mus.cc
@@ -108,9 +108,11 @@ void WindowTreeHostMus::SetBoundsFromServer(const gfx::Rect& bounds) {
   SetBoundsInPixels(bounds);
 }
 
-void WindowTreeHostMus::SetClientArea(const gfx::Insets& insets) {
+void WindowTreeHostMus::SetClientArea(
+    const gfx::Insets& insets,
+    const std::vector<gfx::Rect>& additional_client_area) {
   delegate_->OnWindowTreeHostClientAreaWillChange(this, insets,
-                                                  std::vector<gfx::Rect>());
+                                                  additional_client_area);
 }
 
 void WindowTreeHostMus::SetHitTestMask(const base::Optional<gfx::Rect>& rect) {