Adjust Chrome API calls to use Promises where possible

[kzar]

Background

For version 3 of Chrome's extension manifest format, one planned change is to switch from callbacks to Promises for the Chrome APIs. ​From the draft spec:

Extension APIs will be promise-based. The older callback version will continue to be supported...

In order to maintain backwards compatibility (and not force developers to rewrite their extension
more than they already have to), providing a callback to an API method will continue to work. If
a callback is provided, a promise will not be returned.
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=== What to change ===
Where possible use Promises instead of callbacks when using the browser.* or chrome.* APIs. If necessary wrap them - see `adblockpluschrome/polyfill.js`.