Change variable order for RootInlineBox and fix size check

Change the order of variables in RootInlineBox to group them by type and
therefor allow better alignment on 64bit windows builds. Also update the
order in SameSizeAsRootInlineBox and re-enable the size check on Windows
builds.

TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/346003004

git-svn-id: svn://svn.chromium.org/blink/trunk@176695 bbb929c8-8fbe-4397-9dbb-9b2b20218538