Closure compiling renames external resources methods

[mkhatib]

Reproduce:

• Build a local master with gulp build --fortesting && gulp dist --fortesting
• Run gulp
• Navigate to ads.amp.min.html example in the browser
• Scroll toward Criteo ad
• Notice the following error in the console.

criteo.js:25 - Uncaught TypeError: Criteo.l is not a function

This points to this code. Closure compiler seems to be renaming Criteo.DisplayAd to Criteo.l. Similar errors might be happening elsewhere.