Revert "Revert "Implement call combiner""
This reverts commit bf19961d0a49b43cb528392efeb4880eeebb9b5e.
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index 91c149e..c2e369a 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -948,6 +948,7 @@
src/core/lib/http/format_request.h \
src/core/lib/http/httpcli.h \
src/core/lib/http/parser.h \
+src/core/lib/iomgr/call_combiner.h \
src/core/lib/iomgr/closure.h \
src/core/lib/iomgr/combiner.h \
src/core/lib/iomgr/endpoint.h \