Experimental scanner: keep track of which strings / identifiers contain an escape.

src/lexer/experimental-scanner.h

Index: src/lexer/experimental-scanner.h
diff --git a/src/lexer/experimental-scanner.h b/src/lexer/experimental-scanner.h
index 05423c6b669a70eaa46c7f7f9e4be26aa7c2ed13..ef65ee5cc1e199559dacadaedd8de47df9ea2e48 100644
--- a/src/lexer/experimental-scanner.h
+++ b/src/lexer/experimental-scanner.h
@@ -188,8 +188,9 @@ class ScannerBase {
   // we need to decide if pos is counted in characters or in bytes.
   virtual void SeekForward(int pos) = 0;
 
-  // Scans the input as a regular expression pattern, previous
-  // character(s) must be /(=). Returns true if a pattern is scanned.
+  // Scans the input as a regular expression pattern, previous character(s) must
+  // be /(=). Returns true if a pattern is scanned. FIXME: this won't work for
+  // utf-8 newlines.
   virtual bool ScanRegExpPattern(bool seen_equal) = 0;
   // Returns true if regexp flags are scanned (always since flags can
   // be empty).
@@ -200,6 +201,7 @@ class ScannerBase {
     Token::Value token;
     int beg_pos;
     int end_pos;
+    bool has_escapes;
   };
 
   virtual void Scan() = 0;