- polyfill sheet added while processing styles; should help avoid FUOC
 - add pseudos shimming: ::x-special converted to [pseudo=x-special]
 - add upper bound encapsulation: instead of shimming .foo via x-name .foo we now add x-name to each node in the element's template and shim via .foo[x-name]
polyfill :scope inside @host rules.
make strict polyfill styling optional via Polymer.strictPolyfillStyling flag.
ensure polyfill for :scope is always at the start of the selector
handle content property specially due to issue with cssom removing quotes.
more tests for @host styling.
support [is=name] syntax.
fix content property so it round-trips correctly (https://code.google.com/p/chromium/issues/detail?id=247231)
test for @polyfill
 - @polyfill can contain @host
 - some refactoring of scope application
add test for host styles for type extension elements
support [is=name] syntax for @host styles; minor factoring
element stylesheet refactoring (wip)
 - only fix content property if it is set
 - correctly scope [is=name] .foo
 - ensure controller styles are added only 1x per controller
 - add 1 style element for stylesheets
 - slight refactoring
Merge branch 'shimStyling'