[EFL][WK2] Use C API inside ewk_window_features

[EFL][WK2] Use C API inside ewk_window_features
https://bugs.webkit.org/show_bug.cgi?id=107924

Reviewed by Sam Weinig.

Use C API inside ewk_window_features instead of accessing
internal C++ classes directly, to avoid violating API
layering.

* UIProcess/API/efl/EwkView.cpp:
(EwkView::createNewPage):
* UIProcess/API/efl/EwkView.h:
(EwkView):
* UIProcess/API/efl/ewk_window_features.cpp:
(EwkWindowFeatures::EwkWindowFeatures):
(getWindowFeatureValue):
(EwkWindowFeatures::getWindowFeatureBoolValue):
(EwkWindowFeatures::getWindowFeatureDoubleValue):
(ewk_window_features_geometry_get):
* UIProcess/API/efl/ewk_window_features_private.h:
(EwkWindowFeatures::create):
(EwkWindowFeatures::geometry):
(EwkWindowFeatures::setGeometry):
(EwkWindowFeatures):
* UIProcess/efl/PageUIClientEfl.cpp:
(WebKit::PageUIClientEfl::createNewPage):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@141274 268f45cc-cd09-0410-ab3c-d52691b4dbfc