[parser] Lift template literal invalid escape restriction

src/parsing/scanner.h

Index: src/parsing/scanner.h
diff --git a/src/parsing/scanner.h b/src/parsing/scanner.h
index 075b9ca6b2ba0c1d9468e7eef7e3598c85a5cd36..a2996e420a1c3fe8908cfd316bad4564f3a19ffe 100644
--- a/src/parsing/scanner.h
+++ b/src/parsing/scanner.h
@@ -209,10 +209,17 @@ class Scanner {
   // (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()).