inputflinger: add missing <functional> include

Bug: 175635923
Test: treehugger
Change-Id: Ieb7828b26613c3b5470c9b76f31ad1b6b09d9445
Merged-In: Ieb7828b26613c3b5470c9b76f31ad1b6b09d9445
diff --git a/services/inputflinger/BlockingQueue.h b/services/inputflinger/BlockingQueue.h
index 5693848..f848c82 100644
--- a/services/inputflinger/BlockingQueue.h
+++ b/services/inputflinger/BlockingQueue.h
@@ -17,6 +17,7 @@
 #pragma once
 
 #include <condition_variable>
+#include <functional>
 #include <list>
 #include <mutex>
 #include <optional>