https://bugs.webkit.org/show_bug.cgi?id=123323

Reviewed by Sam Weinig.

WebPageProxy contains an enum and typedef that provide a bitfield
of flags describing the visibility of the view containing the page.
We're going to want to use this bitfield in a message to the
WebProcess, so moving out from the UIProcess to shared code.
Creating struct 'ViewState' to scope the enum and typedef.
Renamed ViewStateFlags to ViewState::Flags, and removed redundant
'View' from enum entries.

* Shared/ViewState.h: Added.
* UIProcess/API/mac/WKView.mm:
(-[WKView becomeFirstResponder]):
(-[WKView resignFirstResponder]):
(-[WKView viewDidMoveToWindow]):
(-[WKView _windowDidBecomeKey:]):
(-[WKView _windowDidResignKey:]):
(-[WKView _windowDidMiniaturize:]):
(-[WKView _windowDidDeminiaturize:]):
(-[WKView _windowDidOrderOffScreen:]):
(-[WKView _windowDidOrderOnScreen:]):
(-[WKView _windowDidChangeOcclusionState:]):
(-[WKView viewDidHide]):
(-[WKView viewDidUnhide]):
(-[WKView _activeSpaceDidChange:]):
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::viewStateDidChange):
* UIProcess/WebPageProxy.h:
* WebKit2.xcodeproj/project.pbxproj:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158028 268f45cc-cd09-0410-ab3c-d52691b4dbfc