[esnext] implement frontend changes for async/await proposal

src/parsing/scanner.cc

Index: src/parsing/scanner.cc
diff --git a/src/parsing/scanner.cc b/src/parsing/scanner.cc
index 698cb5e9058b66df6228257768b69db5ff33268c..f722e93b7fe0c74f794307a28a097116ad4b0826 100644
--- a/src/parsing/scanner.cc
+++ b/src/parsing/scanner.cc
@@ -249,6 +249,8 @@ Token::Value Scanner::Next() {
   if (V8_UNLIKELY(next_next_.token != Token::UNINITIALIZED)) {
     next_ = next_next_;
     next_next_.token = Token::UNINITIALIZED;
+    has_line_terminator_before_next_ = has_line_terminator_before_next2_;
+    has_multiline_comment_before_next_ = has_multiline_comment_before_next2_;
     return current_.token;
   }
   has_line_terminator_before_next_ = false;
@@ -274,7 +276,13 @@ Token::Value Scanner::PeekAhead() {
     return next_next_.token;
   }
   TokenDesc prev = current_;
+  bool has_line_terminator_before_next = has_line_terminator_before_next_;
+  bool has_multiline_comment_before_next = has_multiline_comment_before_next_;
   Next();
+  has_line_terminator_before_next2_ = has_line_terminator_before_next_;
+  has_multiline_comment_before_next2_ = has_multiline_comment_before_next_;
+  has_line_terminator_before_next_ = has_line_terminator_before_next;
+  has_multiline_comment_before_next_ = has_multiline_comment_before_next;
   Token::Value ret = next_.token;
   next_next_ = next_;
   next_ = current_;
@@ -1468,6 +1476,15 @@ const AstRawString* Scanner::NextSymbol(AstValueFactory* ast_value_factory) {
   return ast_value_factory->GetTwoByteString(next_literal_two_byte_string());
 }
 
+const AstRawString* Scanner::NextNextSymbol(
+    AstValueFactory* ast_value_factory) {
+  DCHECK(next_next_.token != Token::UNINITIALIZED);
+  LiteralBuffer* literal = next_next_.literal_chars;
+  if (literal->is_one_byte()) {
+    return ast_value_factory->GetOneByteString(literal->one_byte_literal());
+  }
+  return ast_value_factory->GetTwoByteString(literal->two_byte_literal());
+}
 
 const AstRawString* Scanner::CurrentRawSymbol(
     AstValueFactory* ast_value_factory) {