Add the class FilterTargetSwitcher

[shallawa]

5a02a23

Add the class FilterTargetSwitcher
https://bugs.webkit.org/show_bug.cgi?id=246822

Reviewed by Simon Fraser.

This class will manage applying a filter to a certain area of drawings with the
minimum changes in the existing code. All it needs is a set of callbacks in the
existing caller class. And the caller adds a line like this to the drawing
function:

        FilterTargetSwitcher targetSwitcher(*this, bounds);

The constructor of FilterTargetSwitcher will ask the client if there a filter to
apply or not. If there is a filter, it will switch the drawing to a temporary
ImageBuffer. The client has to make sure all the drawing code from now on will
use the context of this ImageBuffer. The destructor will apply the filter to the
temporary ImageBuffer and then composite filtered ImageBuffer back to the client
drawing context.

* Source/WebCore/Sources.txt:
* Source/WebCore/WebCore.xcodeproj/project.pbxproj:
* Source/WebCore/platform/graphics/filters/FilterTargetSwitcher.cpp: Added.
(WebCore::FilterTargetSwitcher::FilterTargetSwitcher):
(WebCore::FilterTargetSwitcher::~FilterTargetSwitcher):
(WebCore::FilterTargetSwitcher::drawingContext const):
(WebCore::FilterTargetSwitcher::outsets const):
* Source/WebCore/platform/graphics/filters/FilterTargetSwitcher.h: Added.

Canonical link: https://commits.webkit.org/255802@main

56c32d1

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

[webkit-early-warning-system]

EWS run on current version of this PR (hash 56c32d1)

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

[webkit-commit-queue]

Committed 255802@main (5a02a23): https://commits.webkit.org/255802@main

Reviewed commits have been landed. Closing PR #5596 and removing active labels.