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

services/navigation/view_impl.cc

Index: services/navigation/view_impl.cc
diff --git a/services/navigation/view_impl.cc b/services/navigation/view_impl.cc
index 578cb90093b4579d4e69f3a38aebca3edf09b9aa..655ccaa9c3ab1a2ca585887427d3f493c78dcd35 100644
--- a/services/navigation/view_impl.cc
+++ b/services/navigation/view_impl.cc
@@ -300,11 +300,6 @@ void ViewImpl::OnLostConnection(aura::WindowTreeClient* client) {
 void ViewImpl::OnPointerEventObserved(const ui::PointerEvent& event,
                                       aura::Window* target) {}
 
-aura::client::CaptureClient* ViewImpl::GetCaptureClient() {
-  // TODO: wire this up. This typically comes from WMState.
-  return nullptr;
-}
-
 aura::PropertyConverter* ViewImpl::GetPropertyConverter() {
   // TODO: wire this up.
   return nullptr;