[EFL][WK2] defaultTextEncodingName should be stored as a member variable of EwkSettings

https://bugs.webkit.org/show_bug.cgi?id=127420

Reviewed by Gyuyoung Kim.

As the defaultTextEncodingName is returned as a local WKEinaSharedString variable,
the stringshared data is de-refed by eina_stringshare_del().
To maintain the reference counter, the defaultTextEncodingName should be stored
as a member variable of EwkSettings class.

* UIProcess/API/efl/ewk_settings.cpp:
(ewk_settings_encoding_detector_enabled_get): Reordering.
(ewk_settings_default_text_encoding_name_set):
(ewk_settings_default_text_encoding_name_get):
(EwkSettings::setDefaultTextEncodingName):
(EwkSettings::defaultTextEncodingName):
* UIProcess/API/efl/ewk_settings_private.h:
(EwkSettings::EwkSettings): Add m_defaultTextEncodingName and setter/getter methods.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@162584 268f45cc-cd09-0410-ab3c-d52691b4dbfc