Add missing assert.h include

Bug: http://b/175635923
Test: treehugger
Change-Id: I654620dff0b087a3c5d1cd4735f9277738ffbc51
diff --git a/services/surfaceflinger/Scheduler/VSyncReactor.cpp b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
index bdcab51..665a7ee 100644
--- a/services/surfaceflinger/Scheduler/VSyncReactor.cpp
+++ b/services/surfaceflinger/Scheduler/VSyncReactor.cpp
@@ -19,6 +19,7 @@
 #define LOG_TAG "VSyncReactor"
 //#define LOG_NDEBUG 0
 
+#include <assert.h>
 #include <cutils/properties.h>
 #include <log/log.h>
 #include <utils/Trace.h>