Consolidate all the one time initialization functions into a single InitializeWebKit2() super function
https://bugs.webkit.org/show_bug.cgi?id=106161

Reviewed by Simon Fraser.

Adds InitializeWebKit2 and uses it.

* CMakeLists.txt:
* GNUmakefile.list.am:
* NetworkProcess/NetworkProcess.cpp:
(WebKit::NetworkProcess::initializeNetworkProcess):
* NetworkProcess/mac/NetworkProcessInitialization.mm:
(WebKit::initializeNetworkProcess):
* PluginProcess/mac/PluginProcessMainMac.mm:
(WebKit::PluginProcessMain):
* Shared/WebKit2Initialize.cpp: Copied from Source/WebKit2/NetworkProcess/mac/NetworkProcessInitialization.mm.
(WebKit::InitializeWebKit2):
* Shared/WebKit2Initialize.h: Copied from Source/WebKit2/NetworkProcess/mac/NetworkProcessInitialization.mm.
(WebKit):
* SharedWorkerProcess/mac/SharedWorkerProcessMainMac.mm:
(WebKit::SharedWorkerProcessMain):
* Target.pri:
* WebKit2.xcodeproj/project.pbxproj:
* WebProcess/WebProcess.cpp:
(WebKit::WebProcess::WebProcess):
* WebProcess/mac/WebProcessInitialization.mm:
(WebKit::initializeWebProcess):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@138881 268f45cc-cd09-0410-ab3c-d52691b4dbfc