https://bugs.webkit.org/show_bug.cgi?id=126356

Reviewed by Sam Weinig.

This will be necessary to move control of process suppression to the WebProcess.
IsVisuallyIdle implies the process has stopped painting, or painted rects are
occluded and not actually being composited. State is provided on a per
WindowServer connection basis, and as such may produce (safe) false positives.

* Shared/ViewState.h:
    - added IsVisuallyIdle.
* UIProcess/API/mac/PageClientImpl.h:
* UIProcess/API/mac/PageClientImpl.mm:
(WebKit::PageClientImpl::isVisuallyIdle):
    - added, on mac checks WindowServerConnection.
* UIProcess/PageClient.h:
(WebKit::PageClient::isVisuallyIdle):
    - base implementation purely based on isViewVisible.
* UIProcess/WebContext.cpp:
(WebKit::WebContext::windowServerConnectionStateChanged):
    - broadcast the state change.
* UIProcess/WebContext.h:
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::updateViewState):
(WebKit::WebPageProxy::viewStateDidChange):
    - propagate IsVisuallyIdle.
* UIProcess/WebProcessProxy.cpp:
(WebKit::WebProcessProxy::windowServerConnectionStateChanged):
    - broadcast the state change.
* UIProcess/WebProcessProxy.h:
    - add windowServerConnectionStateChanged.
* UIProcess/mac/WebContextMac.mm:
(WebKit::WebContext::updateProcessSuppressionStateOfGlobalChildProcesses):
    - moved from static in fle to static member of class.
(WebKit::WebContext::platformInitialize):
    - no need to enableOcclusionNotifications.
(WebKit::WebContext::canEnableProcessSuppressionForNetworkProcess):
(WebKit::WebContext::canEnableProcessSuppressionForWebProcess):
(WebKit::WebContext::canEnableProcessSuppressionForGlobalChildProcesses):
    - changed to call WindowServerConnection.
(WebKit::WebContext::processSuppressionEnabledChanged):
    - don't remove/reregister occlusion notifications.
* UIProcess/mac/WindowServerConnection.h: Added.
(WebKit::WindowServerConnection::applicationIsOccluded):
(WebKit::WindowServerConnection::applicationWindowModificationsHaveStopped):
    - accessors.
* UIProcess/mac/WindowServerConnection.mm: Added.
(WebKit::WindowServerConnection::applicationBecameOccluded):
(WebKit::WindowServerConnection::applicationWindowModificationsStopped):
(WebKit::WindowServerConnection::applicationBecameVisible):
(WebKit::WindowServerConnection::applicationWindowModificationsStarted):
    - handle notifications from the WindowServer.
(WebKit::WindowServerConnection::windowServerConnectionStateChanged):
    - broadcast the state change.
(WebKit::WindowServerConnection::shared):
    - accessor for singleton object.
(WebKit::WindowServerConnection::WindowServerConnection):
    - constructor inizializes fields & register notification handlers.
* WebKit2.xcodeproj/project.pbxproj:
    - added new files.
* config.h:
    - added HAVE_WINDOW_SERVER_OCCLUSION_NOTIFICATIONS.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@161246 268f45cc-cd09-0410-ab3c-d52691b4dbfc