https://bugs.webkit.org/show_bug.cgi?id=126180

Reviewed by Darin Adler.

Source/WebCore:

* WebCore.xcodeproj/project.pbxproj:
* dom/EventNames.h:
(WebCore::EventNames::isGestureEventType): Added.
* page/AlternativeTextClient.h: Do not define WTF_USE_DICTATION_ALTERNATIVES when building for iOS.
* page/Chrome.cpp:
(WebCore::Chrome::Chrome):
(WebCore::Chrome::dispatchViewportPropertiesDidChange): Added; guarded by PLATFORM(IOS).
(WebCore::Chrome::setCursor): Make this an empty function when building for iOS.
(WebCore::Chrome::setCursorHiddenUntilMouseMoves): Ditto.
(WebCore::Chrome::didReceiveDocType): Added; iOS-specific.
* page/Chrome.h:
(WebCore::Chrome::setDispatchViewportDataDidChangeSuppressed): Added; guarded by PLATFORM(IOS).
* page/ChromeClient.h:
(WebCore::ChromeClient::didFlushCompositingLayers): Added; guarded by PLATFORM(IOS).
(WebCore::ChromeClient::fetchCustomFixedPositionLayoutRect): Added; guarded by PLATFORM(IOS).
(WebCore::ChromeClient::updateViewportC...