Properly skip expressions that contain the operator as.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 10146)
+++ runtime/vm/parser.cc	(working copy)
@@ -8832,8 +8832,11 @@
 
 void Parser::SkipBinaryExpr() {
   SkipUnaryExpr();
-  while (Token::Precedence(Token::kOR) <= Token::Precedence(CurrentToken()) &&
-      Token::Precedence(CurrentToken()) <= Token::Precedence(Token::kMUL)) {
+  const int min_prec = Token::Precedence(Token::kOR);
+  const int max_prec = Token::Precedence(Token::kMUL);
+  while (((min_prec <= Token::Precedence(CurrentToken())) &&
+      (Token::Precedence(CurrentToken()) <= max_prec)) ||
+      IsLiteral("as")) {
     ConsumeToken();
     SkipUnaryExpr();
   }