clang-format: [JS] Do not collapse short interfaces.

Patch by Martin Probst.

llvm-svn: 236485
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index a7d8dd3..0c36dce 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -547,6 +547,12 @@
   verifyFormat("class C extends p.P implements i.I {}");
 }
 
+TEST_F(FormatTestJS, InterfaceDeclarations) {
+  verifyFormat("interface I {\n"
+               "  x: string;\n"
+               "}");
+}
+
 TEST_F(FormatTestJS, MetadataAnnotations) {
   verifyFormat("@A\nclass C {\n}");
   verifyFormat("@A({arg: 'value'})\nclass C {\n}");