[es7] Implement async functions parsing

src/scanner.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #include "src/scanner.h"
 
 #include <stdint.h>
 
@@ skipping 1096 matching lines @@
     return cp;
   }
   return ScanHexNumber<capture_raw>(4);
 }
 
 
 // ----------------------------------------------------------------------------
 // Keyword Matcher
 
 #define KEYWORDS(KEYWORD_GROUP, KEYWORD)                    \
+  KEYWORD_GROUP('a')                                        \
+  KEYWORD("async", Token::ASYNC)                            \
   KEYWORD_GROUP('b')                                        \
   KEYWORD("break", Token::BREAK)                            \
   KEYWORD_GROUP('c')                                        \
   KEYWORD("case", Token::CASE)                              \
   KEYWORD("catch", Token::CATCH)                            \
   KEYWORD("class", Token::CLASS)                            \
   KEYWORD("const", Token::CONST)                            \
   KEYWORD("continue", Token::CONTINUE)                      \
   KEYWORD_GROUP('d')                                        \
   KEYWORD("debugger", Token::DEBUGGER)                      \
@@ skipping 506 matching lines @@
     backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<uint8_t>(one_byte_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 
 }  // namespace internal
 }  // namespace v8