[UI-side compositing] The UI process needs to be able to compute the current unobscuredContentRect on the fly

[smfr]

6e2e8fe

[UI-side compositing] The UI process needs to be able to compute the current unobscuredContentRect on the fly
https://bugs.webkit.org/show_bug.cgi?id=253089
Include a Radar link (OOPS!).

Reviewed by NOBODY (OOPS!).

WIP

* Source/WebKit/UIProcess/Cocoa/WebPageProxyCocoa.mm:
(WebKit::WebPageProxy::didCommitLayerTree):
(WebKit::adjustedUnexposedEdge):
(WebKit::adjustedUnexposedMaxEdge):
(WebKit::WebPageProxy::computeLayoutViewportRect const):
(WebKit::WebPageProxy::unconstrainedLayoutViewportRect const):
* Source/WebKit/UIProcess/DrawingAreaProxy.h:
(WebKit::DrawingAreaProxy::adjustTransientZoom):
(WebKit::DrawingAreaProxy::commitTransientZoom):
* Source/WebKit/UIProcess/PageClient.h:
* Source/WebKit/UIProcess/RemoteLayerTree/mac/RemoteLayerTreeDrawingAreaProxyMac.h:
* Source/WebKit/UIProcess/RemoteLayerTree/mac/RemoteLayerTreeDrawingAreaProxyMac.mm:
(WebKit::RemoteLayerTreeDrawingAreaProxyMac::didCommitLayerTree):
(WebKit::RemoteLayerTreeDrawingAreaProxyMac::adjustTransientZoom):
(WebKit::RemoteLayerTreeDrawingAreaProxyMac::commitTransientZoom):
(WebKit::RemoteLayerTreeDrawingAreaProxyMac::computeUnobscuredContentRect):
* Source/WebKit/UIProcess/ViewGestureController.cpp:
(WebKit::ViewGestureController::scaledMagnificationOrigin):
(WebKit::ViewGestureController::didCollectGeometryForMagnificationGesture):
(WebKit::ViewGestureController::applyMagnification):
(WebKit::ViewGestureController::endMagnificationGesture):
* Source/WebKit/UIProcess/WebPageProxy.h:
* Source/WebKit/UIProcess/ios/WebPageProxyIOS.mm:
(WebKit::adjustedUnexposedEdge): Deleted.
(WebKit::adjustedUnexposedMaxEdge): Deleted.
(WebKit::WebPageProxy::computeLayoutViewportRect const): Deleted.
(WebKit::WebPageProxy::unconstrainedLayoutViewportRect const): Deleted.
* Source/WebKit/UIProcess/mac/PageClientImplMac.h:
* Source/WebKit/UIProcess/mac/PageClientImplMac.mm:
(WebKit::PageClientImpl::minimumZoomScale const):
(WebKit::PageClientImpl::documentRect const):
* Source/WebKit/UIProcess/mac/TiledCoreAnimationDrawingAreaProxy.h:
* Source/WebKit/UIProcess/mac/TiledCoreAnimationDrawingAreaProxy.mm:
(WebKit::TiledCoreAnimationDrawingAreaProxy::adjustTransientZoom):
(WebKit::TiledCoreAnimationDrawingAreaProxy::commitTransientZoom):
* Source/WebKit/UIProcess/mac/ViewGestureControllerMac.mm:
(WebKit::ViewGestureController::handleMagnificationGestureEvent):
(WebKit::ViewGestureController::didCollectGeometryForSmartMagnificationGesture):

6e2e8fe

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	❌ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	❌ 🛠 ios-sim	✅ 🛠 mac-AS-debug	❌ 🛠 gtk
✅ 🧪 webkitperl	❌ 🧪 ios-wk2	✅ 🧪 api-mac	❌ 🧪 gtk-wk2
	❌ 🧪 api-ios	✅ 🧪 mac-wk1	❌ 🧪 api-gtk
	❌ 🛠 tv	✅ 🧪 mac-wk2
	❌ 🛠 tv-sim	✅ 🧪 mac-AS-debug-wk2
	❌ 🛠 watch	✅ 🧪 mac-wk2-stress
	❌ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash f7cfcec)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	❌ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
	✅ 🛠 ios-sim	❌ 🛠 mac-AS-debug	❌ 🛠 gtk
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	❌ 🧪 api-mac	❌ 🧪 gtk-wk2
	✅ 🧪 api-ios	❌ 🧪 mac-wk1	❌ 🧪 api-gtk
	✅ 🛠 tv	❌ 🧪 mac-wk2
	✅ 🛠 tv-sim	❌ 🧪 mac-AS-debug-wk2
	✅ 🛠 watch	❌ 🧪 mac-wk2-stress
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash 6e2e8fe)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	❌ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	❌ 🛠 ios-sim	✅ 🛠 mac-AS-debug	❌ 🛠 gtk
✅ 🧪 webkitperl	❌ 🧪 ios-wk2	✅ 🧪 api-mac	❌ 🧪 gtk-wk2
	❌ 🧪 api-ios	✅ 🧪 mac-wk1	❌ 🧪 api-gtk
	❌ 🛠 tv	✅ 🧪 mac-wk2
	❌ 🛠 tv-sim	✅ 🧪 mac-AS-debug-wk2
	❌ 🛠 watch	✅ 🧪 mac-wk2-stress
	❌ 🛠 watch-sim