deliverChangeRecords delivers changes which are under delivery

[miyconst]

If deliverChangeRecords method was called from an observer, it should not try to deliver the changes which were sent to the observer.

Test case:

it("should not deliver changes already being under delivery", function (done) {
    var count = 0;
    var obj = { value: 1 };
    var callback = function () {
        count++;

        if (count > 1) {
            done(new Error("deliverChangeRecords should not deliver same changes more then once!"));
            return;
        }

        Object.deliverChangeRecords(callback);
    };

    Object.observe(obj, callback);
    obj.value++;

    setTimeout(function () {
        done();
    }, 10);
});

Note: this test case works fine under npm, but fails under FF and IE.

The fix is very simple.
Here https://github.com/MaxArt2501/object-observe/blob/master/dist/object-observe.js#L514
replace:

if (hdata.changeRecords.length) {
    handler(hdata.changeRecords);
    hdata.changeRecords = [];
}

with:

if (hdata.changeRecords.length) {
    handler(hdata.changeRecords.splice(0, hdata.changeRecords.length));
}

[MaxArt2501]

Another good catch, thank you.
About the fix: to avoid using a slow method like splice, let's just keep a reference to the array:

if (hdata.changeRecords.length) {
    var records = hdata.changeRecords;
    hdata.changeRecords = [];
    handler(records);
}

I'll implement this later.

[miyconst]

Sure, I just didn't investigate whether it is safe to replace entire array.