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