Fix leak introduced in r194610, found by LSan.

LSan folks: LSan pointed to
    #0 0x4953e0 in operator new[](unsigned long) llvm/projects/compiler-rt/lib/asan/asan_new_delete.cc:64
    #1 0x7fb82af5372f in clang::RewriteRope::MakeRopeString(char const*, char const*) llvm/tools/clang/lib/Rewrite/Core/RewriteRope.cpp:796
instead of to the actual leak, which made tracking this down slower than
it could have been.

llvm-svn: 207031

clang/include/clang/Index/CommentToXML.h

@@ -29,6 +29,7 @@ class CommentToXMLConverter {
 
 public:
   CommentToXMLConverter() : FormatContext(0), FormatInMemoryUniqueId(0) {}
+  ~CommentToXMLConverter();
 
   void convertCommentToHTML(const comments::FullComment *FC,
                             SmallVectorImpl<char> &HTML,

clang/lib/Index/CommentToXML.cpp

@@ -1136,6 +1136,10 @@ void CommentASTToXMLConverter::appendToResultWithCDATAEscaping(StringRef S) {
   Result << "]]>";
 }
 
+CommentToXMLConverter::~CommentToXMLConverter() {
+  delete FormatContext;
+}
+
 void CommentToXMLConverter::convertCommentToHTML(const FullComment *FC,
                                                  SmallVectorImpl<char> &HTML,
                                                  const ASTContext &Context) {