Experimental parser: set start_ properly after illegal token.

test/lexer/cornercases/utf-endlines.js

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+// Flags: --utf8to16
+
 // The "-->" at the beginning of a line is a weird SpiderMonkey compatibility
 // hack.
 
 // This file tests if it's recognized after various Unicode new line markers:
 
 // Recognized as a newline (the break keyword not seen).
 "Line feed":
 --> break
 
 // Vertical tab is not recognized as a newline.
@@ skipping 17 matching lines @@
 
 --> debugger
 
 // Recognized as a newline.
 "Line separator":

 --> default
 
 // Recognized as a newline.
 "Paragraph separator":

 --> delete