Introduce runtime function %OptimizeFunctionOnNextCall to manually trigger optimization.

test/mjsunit/regress/regress-3218915.js

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+// Flags: --allow-natives-syntax
+
 // Checks that comma expression in conditional context is processed correctly.
 
 function withCommaExpressionInConditional(x) {
   if (x > 1000) { for (var i = 0; i < 10000; i++) { } }
   var y;
   if (y = x, y > 1) {
     return 'big';
   }
   return (y = x + 1, y > 1) ? 'medium' : 'small';
 }
 
-for (var i = 0; i < 10000; i++) {
+for (var i = 0; i < 5; i++) {
   withCommaExpressionInConditional(i);
 }
+%OptimizeFunctionOnNextCall(withCommaExpressionInConditional);
+withCommaExpressionInConditional(i);
 withCommaExpressionInConditional("1")