Enable ES6 iteration by default

test/mjsunit/es6/regress/regress-crbug-248025.js

 // Copyright 2013 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
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 //       notice, this list of conditions and the following disclaimer.
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 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --harmony-iteration
-
 // Filler long enough to trigger lazy parsing.
 var filler = "//" + new Array(1024).join('x');
 
 // Test that the pre-parser does not crash when the expected contextual
 // keyword as part if a 'for' statement is not and identifier.
 try {
   eval(filler + "\nfunction f() { for (x : y) { } }");
   throw "not reached";
 } catch (e) {
   if (!(e instanceof SyntaxError)) throw e;
 }