Allow \n in GN string literals

tools/gn/parser.cc

 // Copyright (c) 2013 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/parser.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "tools/gn/functions.h"
@@ skipping 44 matching lines @@
     "\n"
     "String literals\n"
     "\n"
     "  A string literal represents a string value consisting of the quoted\n"
     "  characters with possible escape sequences and variable expansions.\n"
     "\n"
     "      string           = `\"` { char | escape | expansion } `\"` .\n"
     "      escape           = `\\` ( \"$\" | `\"` | char ) .\n"
     "      BracketExpansion = \"{\" ( identifier | ArrayAccess | ScopeAccess "
                               ") \"}\" .\n"
-    "      expansion        = \"$\" ( identifier | BracketExpansion ) .\n"
+    "      Hex              = \"0x\" [0-9A-Fa-f][0-9A-Fa-f]\n"
+    "      expansion        = \"$\" ( identifier | BracketExpansion | Hex ) .\n"
     "      char             = /* any character except \"$\", `\"`, or newline "
                              "*/ .\n"
     "\n"
     "  After a backslash, certain sequences represent special characters:\n"
     "\n"
     "          \\\"    U+0022    quotation mark\n"
     "          \\$    U+0024    dollar sign\n"
     "          \\\\    U+005C    backslash\n"
     "\n"
     "  All other backslashes represent themselves.\n"
     "\n"
+    "  To insert an arbitrary byte value, use $0xFF. For example, to\n"
+    "  insert a newline character: \"Line one$0x0ALine two\".\n"
+    "\n"
     "Punctuation\n"
     "\n"
     "  The following character sequences represent punctuation:\n"
     "\n"
     "          +       +=      ==      !=      (       )\n"
     "          -       -=      <       <=      [       ]\n"
     "          !       =       >       >=      {       }\n"
     "                          &&      ||      .       ,\n"
     "\n"
     "Grammar\n"
@@ skipping 666 matching lines @@
         break;
       }
     }
 
     // Suffix comments were assigned in reverse, so if there were multiple on
     // the same node, they need to be reversed.
     if ((*i)->comments() && !(*i)->comments()->suffix().empty())
       const_cast<ParseNode*>(*i)->comments_mutable()->ReverseSuffix();
   }
 }