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

ui/aura/test/aura_test_base.cc

Index: ui/aura/test/aura_test_base.cc
diff --git a/ui/aura/test/aura_test_base.cc b/ui/aura/test/aura_test_base.cc
index 9732917574ed6be64d8001f56fd49ee9ce112072..6d7c340bac14bd51688b4127024bf9e4905c6571 100644
--- a/ui/aura/test/aura_test_base.cc
+++ b/ui/aura/test/aura_test_base.cc
@@ -228,10 +228,6 @@ bool AuraTestBase::IsWindowActive(aura::Window* window) { return false; }
 
 void AuraTestBase::OnWmDeactivateWindow(Window* window) {}
 
-client::CaptureClient* AuraTestBase::GetCaptureClient() {
-  return helper_->capture_client();
-}
-
 PropertyConverter* AuraTestBase::GetPropertyConverter() {
   return &property_converter_;
 }