clang-format: [JS] Support ES6 computed property names.

Before:
  var x = {
        [a]: 1,
    b: 2
  };

After:
  var x = {
    [a]: 1,
    b: 2
  };

llvm-svn: 238544
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index a536926..d95ff9b 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -151,6 +151,11 @@
   // Arrow functions in object literals.
   verifyFormat("var x = {y: (a) => { return a; }};");
   verifyFormat("var x = {y: (a) => a};");
+
+  // Computed keys.
+  verifyFormat("var x = {\n"
+               "  [a]: 1,\n"
+               "};");
 }
 
 TEST_F(FormatTestJS, MethodsInObjectLiterals) {