Made -webkit-box-direction property independent.

Made -webkit-box-direction property independent. Also updated
independent-inheritance-fast-path.html to include webkitBoxDirection.

Also updated make_computed_style_base.py to use 'name_for_methods'
instead of 'upper_camel_name' so that Webkit is removed from the front
of the name when generating method names.

Tested using independent-inheritance-fast-path.html.

BUG=628043

Review-Url: https://codereview.chromium.org/2574063002
Cr-Commit-Position: refs/heads/master@{#438746}
3 files changed