Update the mojom lexer to emit comment tokens.

mojom/mojom_parser/lexer/tokens.go

 // Copyright 2015 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.
 //
 // TokenKinds is a type which describes the kinds of tokens which can be
 // encountered in a mojom file.
 
 package lexer
 
 import (
@@ skipping 49 matching lines @@
         True
         False
         Default
 
         // Constants
         IntConstDec
         IntConstHex
         FloatConst
         Ordinal
         StringLiteral
+
+        // Comments
+        SingleLineComment
+        MultiLineComment
 )
 
 // This method is used to generate user-facing strings in compilation error
 // messages. For example for LBrace we produce the string "'{'". Notice the
 // single-quotes. This will be used for example in an error message that looks
 // like the following:
 // Unexpected token at line 5, column 6: '###'. Expecting '{'.
 func (tokenKind TokenKind) String() string {
         switch tokenKind {
         // Errors
@@ skipping 75 matching lines @@
                 return "decimal integer literal"
         case IntConstHex:
                 return "hex integer literal"
         case FloatConst:
                 return "float literal"
         case Ordinal:
                 return "an ordinal"
         case StringLiteral:
                 return "a string literal"
 
+        case SingleLineComment:
+                return "single line comment"
+        case MultiLineComment:
+                return "multi line comment"
+
         default:
                 // Note(rudominer) It is important to use %d below so as to avoid
                 // re-invoking this method and causing an infinite recursion.
                 return fmt.Sprintf("%d", tokenKind)
         }
 }
 
 type Token struct {
         Kind TokenKind
         Text string
@@ skipping 114 matching lines @@
                 snippetBuffer.WriteString("\x1b[32;1m")
         }
         snippetBuffer.WriteString(strings.Repeat("^", tokenSize))
         if color {
                 // Reset all printing attributes.
                 snippetBuffer.WriteString("\x1b[0m")
         }
         snippet = snippetBuffer.String()
         return
 }