In GrowMode, force the value to the right representation to avoid deopts between storing the length…

test/mjsunit/regress/regress-grow-deopt.js

Index: test/mjsunit/regress/regress-grow-deopt.js
diff --git a/test/mjsunit/regress/regress-385054.js b/test/mjsunit/regress/regress-grow-deopt.js
similarity index 68%
copy from test/mjsunit/regress/regress-385054.js
copy to test/mjsunit/regress/regress-grow-deopt.js
index 115bca0d21989e2a82325aeb66d8c06aa5ab198c..df3a83fe8b9cea5309b9bf810acb60b7c3901708 100644
--- a/test/mjsunit/regress/regress-385054.js
+++ b/test/mjsunit/regress/regress-grow-deopt.js
@@ -4,13 +4,13 @@
 
 // Flags: --allow-natives-syntax
 
-function f(x) {
-  var a = [1, 2];
-  a[x];
-  return a[0 - x];
+function f(a, v) {
+  a[a.length] = v;
 }
 
-f(0);
-f(0);
+var a = [1.4];
+f(a, 1);
+f(a, 2);
 %OptimizeFunctionOnNextCall(f);
-assertEquals(undefined, f(1));
+f(a, {});
+assertEquals(4, a.length);