Isolate timer checking in its own thread
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index 9664234..e50d906 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -1026,6 +1026,8 @@
 src/core/lib/iomgr/timer_generic.h \
 src/core/lib/iomgr/timer_heap.c \
 src/core/lib/iomgr/timer_heap.h \
+src/core/lib/iomgr/timer_manager.c \
+src/core/lib/iomgr/timer_manager.h \
 src/core/lib/iomgr/timer_uv.c \
 src/core/lib/iomgr/timer_uv.h \
 src/core/lib/iomgr/udp_server.c \