clang-format: [JS] Treat "for" as a reserved word after a ".".

Otherwise, clang-format can get confused with statements like:

  x.for = 1;

llvm-svn: 270188
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index 5f60f1d..4572987 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -125,6 +125,7 @@
   verifyFormat("x.class.struct = 1;");
   verifyFormat("x.case = 1;");
   verifyFormat("x.interface = 1;");
+  verifyFormat("x.for = 1;");
   verifyFormat("x.of() = 1;");
   verifyFormat("x.in() = 1;");
   verifyFormat("x.let() = 1;");