I fired up Charles to try and dissect the source but it's a giant pile of obfuscation. Here is everything I could see with executable code. They must be pumping different sections of the game into individual iframes since there are 6 separate html files that mostly have the same code.

http://chrome.angrybirds.com/angrybirds/angrybirds.nocache.j...

http://chrome.angrybirds.com/angrybirds/10C85AF6734FAE7AFB4C...

http://chrome.angrybirds.com/angrybirds/3C8E31D1DD3333197B71...

http://chrome.angrybirds.com/angrybirds/0E4E6E6C7B52064E8C51...

http://chrome.angrybirds.com/angrybirds/F94722960223E26D4BB6...

http://chrome.angrybirds.com/angrybirds/09F8D37830DE81BA93CE...

http://chrome.angrybirds.com/angrybirds/0B93D95B5E595879D28E...

And all of the levels are listed out with the following pattern

http://chrome.angrybirds.com/angrybirds/json/Level1.json

The spritesheet assets are actually larger then they appear in game, however the scaling still looks really good in the final output, I'm surprised how smooth the game ran. http://chrome.angrybirds.com/angrybirds/sprite_sheets/INGAME...