Revert 8942 "Make scanner not accept invalid unicode escapes in identifiers"

src/scanner-base.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 401 matching lines @@
   inline Token::Value Select(uc32 next, Token::Value then, Token::Value else_) {
     Advance();
     if (c0_ == next) {
       Advance();
       return then;
     } else {
       return else_;
     }
   }
 
-  uc32 ScanHexNumber(int expected_length);
+  uc32 ScanHexEscape(uc32 c, int length);
 
   // Return the current source position.
   int source_pos() {
     return source_->pos() - kCharacterLookaheadBufferSize;
   }
 
   UnicodeCache* unicode_cache_;
 
   // Buffers collecting literal strings, numbers, etc.
   LiteralBuffer literal_buffer1_;
@@ skipping 116 matching lines @@
   // line-terminator after the current token, and before the next.
   bool has_multiline_comment_before_next_;
   // Whether we scan 'let' as a keyword for harmony block scoped
   // let bindings.
   bool harmony_block_scoping_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCANNER_BASE_H_