[iOS][WK2] Black web view after un-suspending process
https://bugs.webkit.org/show_bug.cgi?id=134623
<rdar://problem/17513223>

Reviewed by Simon Fraser.

* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::viewStateDidChange):
Add an argument to viewStateDidChange that allows callers (-[WKContentView _applicationWillEnterForeground:])
to force us to wait for a synchronous reply from the Web process after performing a view state change.

(WebKit::WebPageProxy::dispatchViewStateChange):
Move the has-been-in-window-and-now-is-newly-in-window check into dispatchViewStateChange.
Adjust the logic surrounding going into/out of window by factoring out the IsInWindow-did-change check, for clarity.

* UIProcess/WebPageProxy.h:
* UIProcess/ios/WKContentView.mm:
(-[WKContentView _applicationWillEnterForeground:]):
As previously mentioned, wait for a reply when foregrounding.

* WebProcess/WebPage/DrawingArea.h:
* WebProcess/WebPage/mac/RemoteLayerTreeDrawingArea.h:
* WebProcess/WebPage/mac/RemoteLayerTreeDrawingArea.mm:
(WebKit::RemoteLayerTreeDrawingArea::scheduleCompositingLayerFlushImmediately):
(WebKit::RemoteLayerTreeDrawingArea::scheduleCompositingLayerFlush):
(WebKit::RemoteLayerTreeDrawingArea::viewStateDidChange):
Make sure to schedule a commit immediately if the UI process is waiting for a reply.
Previously we assumed that a commit would be scheduled anyway because we would have to reparent the
layer tree, but that doesn't happen in the suspension-without-unparenting case. Also, we want to skip
all throttling in this case.

* WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.h:
* WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.mm:
(WebKit::TiledCoreAnimationDrawingArea::scheduleCompositingLayerFlushImmediately):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170787 268f45cc-cd09-0410-ab3c-d52691b4dbfc