Handle the case where a single-line comment is less than 3 characters long.

mojom/mojom_parser/formatter/printer.go

 // 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.
 
 package formatter
 
 import (
         "bytes"
         "fmt"
         "mojom/mojom_parser/lexer"
@@ skipping 646 matching lines @@
 }
 
 func (p *printer) writeSingleLineComment(comment lexer.Token) {
         if comment.Kind != lexer.SingleLineComment {
                 panic(fmt.Sprintf("This is not a SingleLineComment: %s", comment))
         }
         commentText := comment.Text
 
         // We expect that the first 2 characters are // followed by a space or tab.
         // If the third character is not a space or tab, we insert a space.
-        space := commentText[2]
-        if space != ' ' && space != '\t' {
+        if len(commentText) > 2 && commentText[2] != ' ' && commentText[2] != '\t' {
                 commentText = "// " + commentText[2:]
         }
         p.write(commentText)
 }
 
 func (p *printer) writeMultiLineComment(comment lexer.Token) {
         if comment.Kind != lexer.MultiLineComment {
                 panic(fmt.Sprintf("This is not a MultiLineComment: %s", comment))
         }
 
@@ skipping 266 matching lines @@
 
 // See sort.Interface.
 func (ifs *importedFilesSorter) Less(i, j int) bool {
         return ifs.imports[i].SpecifiedName < ifs.imports[j].SpecifiedName
 }
 
 // See sort.Interface.
 func (ifs *importedFilesSorter) Swap(i, j int) {
         ifs.imports[i], ifs.imports[j] = ifs.imports[j], ifs.imports[i]
 }