https://bugs.webkit.org/show_bug.cgi?id=124058

Reviewed by Sam Weinig.

The WKBrowsingContextHandle class represents a browsing context and can be sent across process boundaries.

* Shared/API/Cocoa/WKBrowsingContextHandle.h: Added.
* Shared/API/Cocoa/WKBrowsingContextHandle.mm: Added.
(-[WKBrowsingContextHandle _initWithPageID:]):
(-[WKBrowsingContextHandle encodeWithCoder:]):
(-[WKBrowsingContextHandle initWithCoder:]):
(+[WKBrowsingContextHandle supportsSecureCoding]):
* Shared/API/Cocoa/WKBrowsingContextHandleInternal.h: Added.
* UIProcess/API/mac/WKBrowsingContextController.mm:
(-[WKBrowsingContextController handle]):
* UIProcess/API/mac/WKBrowsingContextControllerInternal.h:
* UIProcess/API/mac/WKBrowsingContextControllerPrivate.h:
(NS_ENUM):
* WebKit2.xcodeproj/project.pbxproj:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158936 268f45cc-cd09-0410-ab3c-d52691b4dbfc