Phantom optimisations

* Only compute .css('float') once other checks have been
  completed. This saves at least one call per node.
* Pre-compute .css('float') for comparison against 'float'
  and ''. This halves the total number of calls.

Change-Id: Ia33e861e1b83b72a1433001ef98d73d8a294faf7
Merge "Phantom optimisations"