fix circular dependency libnativewindow <-> libui

Bug: 37647680
Bug: 37648355
Test: compile, manual
Change-Id: I9631beea52e23ebb519411f943c6f5062aedd2e5
diff --git a/libs/gui/tests/StreamSplitter_test.cpp b/libs/gui/tests/StreamSplitter_test.cpp
index 80e30da..e2f4948 100644
--- a/libs/gui/tests/StreamSplitter_test.cpp
+++ b/libs/gui/tests/StreamSplitter_test.cpp
@@ -24,6 +24,8 @@
 #include <gui/StreamSplitter.h>
 #include <private/gui/ComposerService.h>
 
+#include <system/window.h>
+
 #include <gtest/gtest.h>
 
 namespace android {