diff -r 000000000000 -r 6474c204b198 browser/devtools/sourceeditor/codemirror/fold/comment-fold.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/sourceeditor/codemirror/fold/comment-fold.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,42 @@
+CodeMirror.registerGlobalHelper("fold", "comment", function(mode) {
+  return mode.blockCommentStart && mode.blockCommentEnd;
+}, function(cm, start) {
+  var mode = cm.getModeAt(start), startToken = mode.blockCommentStart, endToken = mode.blockCommentEnd;
+  if (!startToken || !endToken) return;
+  var line = start.line, lineText = cm.getLine(line);
+
+  var startCh;
+  for (var at = start.ch, pass = 0;;) {
+    var found = at <= 0 ? -1 : lineText.lastIndexOf(startToken, at - 1);
+    if (found == -1) {
+      if (pass == 1) return;
+      pass = 1;
+      at = lineText.length;
+      continue;
+    }
+    if (pass == 1 && found < start.ch) return;
+    if (/comment/.test(cm.getTokenTypeAt(CodeMirror.Pos(line, found + 1)))) {
+      startCh = found + startToken.length;
+      break;
+    }
+    at = found - 1;
+  }
+
+  var depth = 1, lastLine = cm.lastLine(), end, endCh;
+  outer: for (var i = line; i <= lastLine; ++i) {
+    var text = cm.getLine(i), pos = i == line ? startCh : 0;
+    for (;;) {
+      var nextOpen = text.indexOf(startToken, pos), nextClose = text.indexOf(endToken, pos);
+      if (nextOpen < 0) nextOpen = text.length;
+      if (nextClose < 0) nextClose = text.length;
+      pos = Math.min(nextOpen, nextClose);
+      if (pos == text.length) break;
+      if (pos == nextOpen) ++depth;
+      else if (!--depth) { end = i; endCh = pos; break outer; }
+      ++pos;
+    }
+  }
+  if (end == null || line == end && endCh == startCh) return;
+  return {from: CodeMirror.Pos(line, startCh),
+          to: CodeMirror.Pos(end, endCh)};
+});