v8 method inlining

function Foobar() {
    this.abc = 1;
    this.test = function (n) {
        this.abc = n;
    };
    this.runTest = function (N) {
        console.time('foobar speed');
        for (var i = 0; i < N; ++i) {
            this.test(i);
        }
        console.timeEnd('foobar speed');
    };
}

var N = 10000000;
var a = new Foobar(), b = new Foobar(), c = new Foobar();
a.runTest(N); // foobar speed: 18ms
b.runTest(N); // foobar speed: 125ms
c.runTest(N); // foobar speed: 122ms
a.runTest(N); // foobar speed: 14ms
b.runTest(N); // foobar speed: 117ms
c.runTest(N); // foobar speed: 128ms