[WK2] Stop using WKPreferencesPrivate API to toggle FeatureCounter support

[WK2] Stop using WKPreferencesPrivate API to toggle FeatureCounter support
https://bugs.webkit.org/show_bug.cgi?id=139794
<rdar://problem/19266254>

Reviewed by Anders Carlsson.

Stop using WKPreferencesPrivate API to toggle FeatureCounter support
and use WKWebViewConfigurationPrivate API instead. FeatureCounter is
not meant to change state after the view has been created.

* UIProcess/API/C/WKPreferences.cpp:
(WKPreferencesSetFeatureCounterEnabled): Deleted.
(WKPreferencesGetFeatureCounterEnabled): Deleted.
* UIProcess/API/C/WKPreferencesRefPrivate.h:
* UIProcess/API/Cocoa/WKPreferences.mm:
(-[WKPreferences _featureCounterEnabled]): Deleted.
(-[WKPreferences _setFeatureCounterEnabled:]): Deleted.
* UIProcess/API/Cocoa/WKPreferencesPrivate.h:
* UIProcess/API/Cocoa/WKWebView.mm:
(-[WKWebView initWithFrame:configuration:]):
* UIProcess/API/Cocoa/WKWebViewConfiguration.mm:
(-[WKWebViewConfiguration init]):
(-[WKWebViewConfiguration copyWithZone:]):
(-[WKWebViewConfiguration _featureCounterEnabled]):
(-[WKWebViewConfiguration _setFeatureCounterEnabled:]):
* UIProcess/API/Cocoa/WKWebViewConfigurationPrivate.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@177526 268f45cc-cd09-0410-ab3c-d52691b4dbfc