Pre-calculate view scale and text wrap scale for webkit.

In viewport setup time, pre-calculate the more likely view scale
and text wrap scale instead of waiting until ZoomManager's FirstLayout
time.  This is to give webkit better and more correct information, such
as window width/height and inner width/height, when it is doing first layout.

issue: 3382398
Change-Id: I53fb15da43fbede6c03a4f51ec1c50e9a94f0236