Standardize storage.onChanged event when you set the same values.

[regseb]

Hi,

I noticed a difference between Firefox and Chromium on the storage.onChanged event. I don't know if this is the right place, but it might be nice to standardize this behavior. (Or maybe it's just a bug in Firefox or Chromium.)

• In Firefox, the listeners of browser.storage.onChanged are fired when you set the same values.
• In Chromium, the listeners are fired only if you set a different value.

testcase.zip:

• manifest.json:

{
    "manifest_version": 2,
    "name": "Test case",
    "version": "1.0.0",
    "background": {
        "scripts": ["background.js"]
    },
    "permissions": ["storage"]
}

• background.js:

chrome.storage.onChanged.addListener((changes) => {
    console.log(changes);
});
chrome.storage.local.clear(() => {
    chrome.storage.local.set({ foo: "bar" });
    chrome.storage.local.set({ foo: "bar" });
});

[carlosjeurissen]

storage.onChanged indicates the value to actually have been changed. I do not see a use case in which it would be useful to also have the event fire when the value has not changed.

Removing the unneeded event firing seems like a potential performance improvement for Firefox and potentially other browsers.

[xeenon]

Safari also only fires onChanged if the value does change.