Handle -ast-dump-all when passed as the only option.

Patch by Don Hinton

llvm-svn: 305432
diff --git a/clang/test/Coverage/ast-printing.cpp b/clang/test/Coverage/ast-printing.cpp
index e03c517..bcd78be 100644
--- a/clang/test/Coverage/ast-printing.cpp
+++ b/clang/test/Coverage/ast-printing.cpp
@@ -3,6 +3,7 @@
 // RUN: %clang_cc1 -std=c++14 -ast-print %t.1.cpp -o %t.2.cpp
 // RUN: diff %t.1.cpp %t.2.cpp
 // RUN: %clang_cc1 -std=c++14 -ast-dump %s
+// RUN: %clang_cc1 -std=c++14 -ast-dump-all %s
 // RUN: %clang_cc1 -std=c++14 -print-decl-contexts %s
 // RUN: %clang_cc1 -std=c++14 -fdump-record-layouts %s