Revert "Redo "Steps towards making dart2js JS AST templates an indepentent library.""

Investigating failure of dart2js_incremental.

TBR=floitsch@google.com

Review URL: https://codereview.chromium.org//922463002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@43710 260f80e4-7a28-3924-810f-c04153c831b5