clang-format: [JS] keep triple slash directives intact.

Summary:
TypeScript uses triple slash directives of the form:
    /// <reference path="..."/>

For various non-source instructions that should not be wrapped.

Reference:
https://www.typescriptlang.org/docs/handbook/triple-slash-directives.html

Reviewers: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D32997

llvm-svn: 302523
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index 9144fe17..2889753 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -1785,6 +1785,7 @@
   verifyFormat("import {x} from 'x';  // from some location",
                getGoogleJSStyleWithColumns(25));
   verifyFormat("// taze: x from 'location'", getGoogleJSStyleWithColumns(10));
+  verifyFormat("/// <reference path=\"some/location\" />", getGoogleJSStyleWithColumns(10));
 }
 
 TEST_F(FormatTestJS, Exponentiation) {