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

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 75ff387eb6fb0b403970cd28a8d5a6c998592708..b71391bc5bab8f5977235c55f7e570fe3f791b1c 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -234,10 +234,6 @@ void WindowTreeClient::ConnectAsWindowManager() {
   SetWindowTree(std::move(window_tree));
 }
 
-client::CaptureClient* WindowTreeClient::GetCaptureClient() {
-  return delegate_->GetCaptureClient();
-}
-
 void WindowTreeClient::SetCanFocus(Window* window, bool can_focus) {
   DCHECK(tree_);
   DCHECK(window);