Remove WindowTreeClientDelegate::GetCaptureClient() and WindowTreeClient::GetCaptureClient().

ui/aura/mus/window_tree_client_delegate.h

Index: ui/aura/mus/window_tree_client_delegate.h
diff --git a/ui/aura/mus/window_tree_client_delegate.h b/ui/aura/mus/window_tree_client_delegate.h
index 609a05785854c6fd8accfccc5d02dfdd67f333df..e76d2efbac0b596f543f1e0765080ee391e24b38 100644
--- a/ui/aura/mus/window_tree_client_delegate.h
+++ b/ui/aura/mus/window_tree_client_delegate.h
@@ -19,10 +19,6 @@ class Window;
 class WindowTreeClient;
 class WindowTreeHostMus;
 
-namespace client {
-class CaptureClient;
-}
-
 // Interface implemented by an application using mus.
 class AURA_EXPORT WindowTreeClientDelegate {
  public:
@@ -62,10 +58,6 @@ class AURA_EXPORT WindowTreeClientDelegate {
   virtual void OnPointerEventObserved(const ui::PointerEvent& event,
                                       Window* target) = 0;
 
-  // Mus expects a single CaptureClient is used for all WindowTreeHosts. This
-  // returns it. GetCaptureClient() is called from the constructor.
-  virtual client::CaptureClient* GetCaptureClient() = 0;
-
   virtual PropertyConverter* GetPropertyConverter() = 0;
 
  protected: