[iOS] Draw caps lock indicator in password fields

[iOS] Draw caps lock indicator in password fields
https://bugs.webkit.org/show_bug.cgi?id=190565
<rdar://problem/45262343>

Reviewed by Dean Jackson.

Source/WebCore:

Draw the caps lock indicator in a focused password field on iOS. This makes the behavior of password
fields on iOS more closely match the behavior of password fields on Mac. For now, we only draw the
indicator when caps locks is enabled via the hardware keyboard. We will look to support the software
keyboard in a subsequent commit (see <https://bugs.webkit.org/show_bug.cgi?id=191475>).

The majority of this patch is implementing PlatformKeyboardEvent::currentCapsLockState() for iOS.
In Legacy WebKit, the implementation boils down to calling call -[::WebEvent modifierFlags]. In
Modern WebKit the UIProcess is responsible for -[::WebEvent modifierFlags] and passing it the
WebProcess to store such that invocations of PlatformKeyboardEvent::currentCapsLockState() consult
the store in the WebProcess. A smaller part of this patch is having both the legacy and modern
web views listen for keyboard availability changes so as to update the the caps lock state when
a hardware keyboard is detached or attached.

* WebCore.xcodeproj/project.pbxproj:
* page/EventHandler.cpp:
(WebCore::EventHandler::capsLockStateMayHaveChanged const): Extracted from EventHandler::internalKeyEvent()
so that it can shared between WebCore, Modern WebKit, and Legacy WebKit code.
(WebCore::EventHandler::internalKeyEvent): Modified to call capsLockStateMayHaveChanged().
* page/EventHandler.h:
* platform/cocoa/KeyEventCocoa.mm:
(WebCore::PlatformKeyboardEvent::currentCapsLockState): Moved from KeyEventMac.mm.
(WebCore::PlatformKeyboardEvent::getCurrentModifierState): Moved from KeyEventMac.mm.
* platform/ios/KeyEventIOS.mm:
(WebCore::PlatformKeyboardEvent::currentStateOfModifierKeys): Fetch the current modifier state.
(WebCore::PlatformKeyboardEvent::currentCapsLockState): Deleted; we now use the Cocoa implementation.
(WebCore::PlatformKeyboardEvent::getCurrentModifierState): Deleted; we now use the Cocoa implementation.
* platform/ios/WebEvent.h:
* platform/ios/WebEvent.mm:
(+[WebEvent modifierFlags]): Added.
* platform/mac/KeyEventMac.mm:
(WebCore::PlatformKeyboardEvent::currentCapsLockState): Deleted; moved to KeyEventCocoa.mm to be shared
by both Mac and iOS.
(WebCore::PlatformKeyboardEvent::getCurrentModifierState): Deleted; moved to KeyEventCocoa.mm to be shared
by both Mac and iOS.
* rendering/RenderThemeCocoa.h:
* rendering/RenderThemeCocoa.mm:
(WebCore::RenderThemeCocoa::shouldHaveCapsLockIndicator const): Moved from RenderThemeMac.mm.
* rendering/RenderThemeIOS.h:
* rendering/RenderThemeIOS.mm:
(WebCore::RenderThemeIOS::shouldHaveCapsLockIndicator const): Deleted.
* rendering/RenderThemeMac.h:
* rendering/RenderThemeMac.mm:
(WebCore::RenderThemeMac::shouldHaveCapsLockIndicator const): Deleted; moved to RenderThemeCocoa.mm to be
shared by both Mac and iOS.

Source/WebCore/PAL:

Forward declare some more SPI.

* pal/spi/ios/GraphicsServicesSPI.h:
* pal/spi/ios/UIKitSPI.h:

Source/WebKit:

Notify the WebContent process with the current modifer state on window activation changes. Notify
the WebContent process when hardware keyboard availability changes (e.g. a keyboard is attached).

* UIProcess/API/Cocoa/WKWebView.mm:
(-[WKWebView _initializeWithConfiguration:]): Register for hardware keyboard availability changed notifications.
(-[WKWebView dealloc]): Unregister from hardware availability changed notifications.
(hardwareKeyboardAvailabilityChangedCallback): Added.
* UIProcess/WebPageProxy.cpp:
(WebKit::WebPageProxy::updateCurrentModifierState): Compile this code when building for iOS.
* UIProcess/WebPageProxy.h:
* UIProcess/ios/WKContentViewInteraction.mm:
(-[WKContentView _handleKeyUIEvent:]): Update the current modifier state if this event is a hardware
keyboard flags changed event.
* UIProcess/ios/WebPageProxyIOS.mm:
(WebKit::WebPageProxy::hardwareKeyboardAvailabilityChanged): Added.

* WebProcess/WebPage/WebPage.h:
* WebProcess/WebPage/WebPage.messages.in:
* WebProcess/WebPage/ios/WebPageIOS.mm:
(WebKit::WebPage::hardwareKeyboardAvailabilityChanged):
Added new message HardwareKeyboardAvailabilityChanged. Notify the focused HTML input element (if we have
one) that the caps lock state may have changed when we receive message HardwareKeyboardAvailabilityChanged
so that we toggle visibility of the caps lock indicator.

Source/WebKitLegacy/mac:

Update the caps lock state when a hardware keyboard is attached or detached.

* WebView/WebHTMLView.mm:
(hardwareKeyboardAvailabilityChangedCallback): Added.
(-[WebHTMLView initWithFrame:]): Register for hardware keyboard availability changed notifications.
(-[WebHTMLView dealloc]): Unregister from hardware keyboard availability changed notifications.

WebKitLibraries:

Expose some more symbols.

* WebKitPrivateFrameworkStubs/iOS/12/GraphicsServices.framework/GraphicsServices.tbd:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@238047 268f45cc-cd09-0410-ab3c-d52691b4dbfc