Remove WebContext::sharedProcessContext()
https://bugs.webkit.org/show_bug.cgi?id=125437

Reviewed by Dan Bernstein.

* UIProcess/API/ios/WKGeolocationProviderIOS.mm:
* UIProcess/WebContext.cpp:
* UIProcess/WebContext.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160300 268f45cc-cd09-0410-ab3c-d52691b4dbfc