[iOS][WK2] Animated resize incorrectly assumes the layout width is the same as the...

[iOS][WK2] Animated resize incorrectly assumes the layout width is the same as the view width
https://bugs.webkit.org/show_bug.cgi?id=132373
<rdar://problem/16762178>

Reviewed by Tim Horton.

* UIProcess/API/Cocoa/WKWebView.mm:
(-[WKWebView _beginAnimatedResizeWithUpdates:]):
Fix a couple of bugs when the left/right obscured insets change, and/or when the minimum layout size
is narrower than the view itself.

In order:
-We need to perfom and update if the insets change since the unobscuredRect will also change.
-The min/max zoom scale should be based on the minimum layout size, that's the definition of minimum layout size
 in scrollview coordinate :)
-The old web view width in content coordinate could be narrower than the old view bounds if there are left or right
 insets.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@168080 268f45cc-cd09-0410-ab3c-d52691b4dbfc