Introduce runtime function %OptimizeFunctionOnNextCall to manually trigger optimization.

test/mjsunit/regress/regress-1237.js

Index: test/mjsunit/regress/regress-1237.js
diff --git a/test/mjsunit/regress/regress-1237.js b/test/mjsunit/regress/regress-1237.js
index f97f97861fc12319af6dfee5df4d6753cb8ec803..111df803f47cf1266740f54771d29bc97330c1af 100644
--- a/test/mjsunit/regress/regress-1237.js
+++ b/test/mjsunit/regress/regress-1237.js
@@ -25,6 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --allow-natives-syntax
+
 // Deoptimization after a conditional expression in an effect context should
 // not see the value of the expression.
 function observe(x, y) { return x; }
@@ -32,5 +34,8 @@ function test(x) {
   return observe(1, ((x? observe(observe.prototype.x): 'c'), x + 1));
 }
 
-for (var i = 0; i < 10000000; ++i) test(0);
+for (var i = 0; i < 5; ++i) test(0);
+%OptimizeFunctionOnNextCall(test);
+test(0);
+
 test("a");