Layers view: Extract zoom/pan/rotate logic into transorm controller

Also, apply zoom to layer div sizes to keep resulting layers small.

BUG=

Review URL: https://codereview.chromium.org/177353005

git-svn-id: svn://svn.chromium.org/blink/trunk@168552 bbb929c8-8fbe-4397-9dbb-9b2b20218538