Make WKBrowsingContextGroup work with WKObject wrapping

Make WKBrowsingContextGroup work with WKObject wrapping
https://bugs.webkit.org/show_bug.cgi?id=124948

Reviewed by Dan Bernstein.

- Adds mechanism to use the inline data wrapping mechanism when the Objective-C wrapper is created
  by the caller (rather than by Object::newObject).
- Adopts the mechanism for WKBrowsingContextGroup.

* Shared/APIObject.h:
(API::Object::constructInWrapper):
Add a helper which does a forwarding placement-new into the API::Object of the passed in wrapper, after which it sets up m_wrapper.

(API::TypedObject::operator new):
Add a operator new to for placement-new. Also make TypedObject friends with Object so that constructInWrapper can call this.

* Shared/Cocoa/APIObject.mm:
(API::Object::newObject):
Add support for WKBrowsingContextGroup.

* UIProcess/API/mac/WKBrowsingContextGroup.mm:
(-[WKBrowsingContextGroup API::]):
(-[WKBrowsingContextGroup dealloc]):
(-[WKBrowsingContextGroup initWithIdentifier:]):
(-[WKBrowsingContextGroup allowsJavaScript]):
(-[WKBrowsingContextGroup setAllowsJavaScript:]):
(-[WKBrowsingContextGroup allowsJavaScriptMarkup]):
(-[WKBrowsingContextGroup setAllowsJavaScriptMarkup:]):
(-[WKBrowsingContextGroup allowsPlugIns]):
(-[WKBrowsingContextGroup setAllowsPlugIns:]):
(-[WKBrowsingContextGroup addUserStyleSheet:baseURL:whitelistedURLPatterns:blacklistedURLPatterns:mainFrameOnly:]):
(-[WKBrowsingContextGroup removeAllUserStyleSheets]):
(-[WKBrowsingContextGroup addUserScript:baseURL:whitelistedURLPatterns:blacklistedURLPatterns:injectionTime:mainFrameOnly:]):
(-[WKBrowsingContextGroup removeAllUserScripts]):
(-[WKBrowsingContextGroup _pageGroupRef]):
Convert from wrapping the C-SPI type to storing the bits of the wrapped object inline (modeled on WKBackForwardList).

* UIProcess/API/mac/WKBrowsingContextGroupInternal.h: Added.
(WebKit::wrapper):
Add wrapper() helper and declare conformance to the WKObject protocol.

* UIProcess/WebPageGroup.cpp:
(WebKit::WebPageGroup::create):
(WebKit::WebPageGroup::WebPageGroup):
* UIProcess/WebPageGroup.h:
Make the WebPageGroup constructor public (for use with Object::constructInWrapper) and move being set in the webPageGroupMap()
to the constructor.

* WebKit2.xcodeproj/project.pbxproj:
Add new file.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@159824 268f45cc-cd09-0410-ab3c-d52691b4dbfc