Port "Eclipse CDT settings" file generation from GYP to GN

tools/gn/xml_element_writer.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/xml_element_writer.h"
 
 XmlAttributes::XmlAttributes() {}
 
 XmlAttributes::XmlAttributes(const base::StringPiece& attr_key,
                              const base::StringPiece& attr_value) {
@@ skipping 20 matching lines @@
       indent_(indent),
       opening_tag_finished_(false),
       one_line_(true) {
   out << std::string(indent, ' ') << '<' << tag;
   for (auto attribute : attributes)
     out << ' ' << attribute.first << "=\"" << attribute.second << '"';
 }
 
 XmlElementWriter::~XmlElementWriter() {
   if (!opening_tag_finished_) {
-    out_ << "/>" << std::endl;
+    // The XML spec does not require a space before the closing slash. However,
+    // Eclipse is unable to parse XML settings files if there is no space.
+    out_ << " />" << std::endl;
   } else {
     if (!one_line_)
       out_ << std::string(indent_, ' ');
     out_ << "</" << tag_ << '>' << std::endl;
   }
 }
 
 void XmlElementWriter::Text(const base::StringPiece& content) {
   StartContent(false);
   out_ << content;
@@ skipping 18 matching lines @@
     opening_tag_finished_ = true;
 
     if (start_new_line && one_line_) {
       out_ << std::endl;
       one_line_ = false;
     }
   }
 
   return out_;
 }