[macOS] drawFocusIfNeeded() should not expose the user's system accent color

[whsieh]

04c640b

[macOS] drawFocusIfNeeded() should not expose the user's system accent color
https://bugs.webkit.org/show_bug.cgi?id=260102
rdar://105554669

Reviewed by Tim Nguyen.

On macOS, `drawFocusIfNeeded()` currently exposes the user's system accent color via
`RenderTheme::focusRingColor()`. To mitigate fingerprinting risk due to this API for users that have
chosen a non-default system accent color, we make `RenderTheme::focusRingColor()` respect the given
`UseSystemAppearance` state by returning the default system focus ring color on macOS, in the case
where that option is absent. As a result, this means that quirks-mode webpages that use
`-webkit-focus-ring-color` will also no longer be able to determine the user's accent color. This
aligns with existing behavior for the "activeborder" CSS value.

Tests:  fast/canvas/do-not-expose-non-default-focus-ring-color.html
        fast/css/mac/focus-ring-color-should-not-expose-accent-color.html

* LayoutTests/TestExpectations:
* LayoutTests/fast/canvas/do-not-expose-non-default-focus-ring-color-expected.html: Added.
* LayoutTests/fast/canvas/do-not-expose-non-default-focus-ring-color.html: Added.
* LayoutTests/fast/canvas/resources/do-not-expose-non-default-focus-ring-color.js: Added.
(paintIntoSwatch):

Add a test to verify that accent colors can't be read back using canvas 2D; to test this, we render
a simple focus ring to a 2D canvas, use `getImageData` to read it back, and verify that the average
non-transparent pixel values in the resulting image data match even when the accent color is
different (customized using the new `UIScriptController` hook below).

* LayoutTests/fast/css/mac/focus-ring-color-should-not-expose-accent-color-expected-mismatch.html: Added.
* LayoutTests/fast/css/mac/focus-ring-color-should-not-expose-accent-color.html: Added.

Add another test to verify that accent colors (1) are not directly leaked through the use of the
`-webkit-focus-ring-color` CSS property, and (2) enabling system appearance is sufficient to expose
the real focus ring color again.

* LayoutTests/platform/mac-wk2/TestExpectations:
* LayoutTests/resources/ui-helper.js:
(window.UIHelper.isMac):
(window.UIHelper.setAppAccentColor):
* Source/WebCore/PAL/pal/spi/ios/UIKitSPI.h:

Drive-by fix: remove an unnecessary UIKit SPI method declaraction.

* Source/WebCore/rendering/RenderElement.cpp:
(WebCore::RenderElement::paintFocusRing const):

Set `UseSystemAppearance` here to ensure that focus rings still paint with the correct appearance.

* Source/WebCore/rendering/RenderImage.cpp:
(WebCore::RenderImage::paintAreaElementFocusRing):

Set `UseSystemAppearance` here to ensure that focus rings still paint with the correct appearance.

* Source/WebCore/rendering/RenderThemeIOS.mm:
(WebCore::RenderThemeIOS::systemFocusRingColor):
* Source/WebCore/rendering/RenderThemeMac.mm:
(WebCore::defaultFocusRingColor):
(WebCore::RenderThemeMac::platformFocusRingColor const):

This is the main fix — pull the hard-coded value for the focus ring color out into a separate helper
function, which we use in `platformFocusRingColor` if `UseSystemAppearance` is unset.

(WebCore::RenderThemeMac::systemColor const):
* Source/WebCore/testing/Internals.cpp:
(WebCore::Internals::focusRingColor):
* Tools/TestRunnerShared/UIScriptContext/Bindings/UIScriptController.idl:
* Tools/TestRunnerShared/UIScriptContext/UIScriptController.h:
(WTR::UIScriptController::setAppAccentColor):

Add a `UIScriptController` hook to set a custom accent color, using `-_setAccentColor:`. This is
reset to the default value (computed upon initializing the test runner and stored in
`m_defaultAppAccentColor`) between test runs.

* Tools/WebKitTestRunner/InjectedBundle/Bindings/TestRunner.idl:
* Tools/WebKitTestRunner/InjectedBundle/TestRunner.h:
(WTR::TestRunner::isMac const):
* Tools/WebKitTestRunner/TestController.h:
* Tools/WebKitTestRunner/mac/TestControllerMac.mm:
(WTR::TestController::platformInitialize):
(WTR::TestController::platformResetStateToConsistentValues):
* Tools/WebKitTestRunner/mac/UIScriptControllerMac.h:
* Tools/WebKitTestRunner/mac/UIScriptControllerMac.mm:
(WTR::UIScriptControllerMac::setAppAccentColor):

Canonical link: https://commits.webkit.org/266881@main

f9bef82

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

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 9264b30)

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

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 08c5e2a)

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

[nt1m]

nit: I'd use auto instead of Color here.

[whsieh]

Good catch — changed to auto.

Thanks for the review!

[webkit-early-warning-system]

EWS run on current version of this PR (hash f9bef82)

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

[webkit-commit-queue]

Committed 266881@main (04c640b): https://commits.webkit.org/266881@main

Reviewed commits have been landed. Closing PR #16649 and removing active labels.