clang-format: [Proto] Also supports implicit string literal concatenation

llvm-svn: 293995
diff --git a/clang/unittests/Format/FormatTestProto.cpp b/clang/unittests/Format/FormatTestProto.cpp
index 6881af4..41d210a 100644
--- a/clang/unittests/Format/FormatTestProto.cpp
+++ b/clang/unittests/Format/FormatTestProto.cpp
@@ -135,6 +135,9 @@
                "    key: 'a'  //\n"
                "  }\n"
                "];");
+  verifyFormat("optional string test = 1 [default =\n"
+               "                              \"test\"\n"
+               "                              \"test\"];");
 }
 
 TEST_F(FormatTestProto, DoesntWrapFileOptions) {