[parser] Lift template literal invalid escape restriction

src/parsing/scanner.h

 // 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.
 
 #ifndef V8_PARSING_SCANNER_H_
 #define V8_PARSING_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 191 matching lines @@
   // Returns the next token and advances input.
   Token::Value Next();
   // Returns the token following peek()
   Token::Value PeekAhead();
   // Returns the current token again.
   Token::Value current_token() { return current_.token; }
   // Returns the location information for the current token
   // (the token last returned by Next()).
   Location location() const { return current_.location; }
 
+  // This error is specifically an invalid hex or unicode escape sequence.
   bool has_error() const { return scanner_error_ != MessageTemplate::kNone; }
   MessageTemplate::Template error() const { return scanner_error_; }
   Location error_location() const { return scanner_error_location_; }
 
+  void clear_error() {
+    DCHECK(has_error());
+    scanner_error_ = MessageTemplate::kNone;
+    scanner_error_location_ = Location();
+  }
+
   // Similar functions for the upcoming token.
 
   // One token look-ahead (past the token returned by Next()).
   Token::Value peek() const { return next_.token; }
 
   Location peek_location() const { return next_.location; }
 
   bool literal_contains_escapes() const {
     return LiteralContainsEscapes(current_);
   }
@@ skipping 529 matching lines @@
   bool found_html_comment_;
 
   MessageTemplate::Template scanner_error_;
   Location scanner_error_location_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_SCANNER_H_