Upon start-up, uBlock runs all content scripts in manifest.json using
`chrome.tabs.executeScript`. When this API is used, the value of the
last expression is automatically cloned and transferred to the
callback of `chrome.tabs.executeScript`. This is convenient if needed,
and a performance burden otherwise (the latter is the case for uBlock).
There are three content scripts that need to be checked:
- vapi.js
The last expression is often the vAPI object, and it is relatively
expensive to clone this object. This commit sets the value of the
last expression to `void 0` to solve this inefficiency.
- vapi-client.js
No action needed yet; The last expression is `vAPI.shutdown.add(...)`,
which has a void return value.
- contentscript.js
No action needed yet; The last expression is an immediately-invoked
function expression without return value.
