refactor(angular.js): improve trim performance

[sunnylost]

According to Flagrant Badassery's blog http://blog.stevenlevithan.com/archives/faster-trim-javascript and this comparision http://jsperf.com/trim-function, this trim method is faster.

[mary-poppins]

Thanks for the PR!

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Thanks again for your help!

[petebacondarwin]

LGTM. @sunnylost - can you please ensure that you have signed the CLA. Also the commit message should be:

refactor(angular.js): improve trim performance

According to Flagrant Badassery's blog
http://blog.stevenlevithan.com/archives/faster-trim-javascript
and this comparision http://jsperf.com/trim-function, this trim method is faster.

Closes #4406

[sunnylost]

Sorry, I didn't know this, I've just signed the CLA and edited the commit message.

[btford]

@petebacondarwin it might also be good to link to the jsperf and article about the optimization from a code comment.

[petebacondarwin]

@btford - Isn't this what git blame is for?

[btford]

This makes it more accessible for those who don't know how to use git blame (this probably amounts to 99% of people on GH). And AFAIK, there's not a great way to see those annotations on GH.

[petebacondarwin]

Its not great(!) but there is a "blame" button when viewing a file, which leads to a view like this: https://github.com/angular/angular.js/blame/master/src/Angular.js

The only reason I questioned this is that Vojta recently suggested I removed a similar code comment on the grounds that it would be in the commit: https://github.com/angular/angular.js/pull/3331/files#/r6801256