Cherry-pick f2404c1. rdar://121471373

    [iOS] YouTube does not provide an AirPlay button in fullscreen mode
    https://bugs.webkit.org/show_bug.cgi?id=268634
    rdar://121471373

    Reviewed by Brent Fulgham and Aditya Keerthi.

    Add a quirk to disable the Fullscreen API on YouTube.com (and youtube.com embeds).

    * Source/WebCore/page/Quirks.cpp:
    (WebCore::Quirks::shouldDisableElementFullscreenQuirk const):

    Canonical link: https://commits.webkit.org/274117@main

Identifier: 272448.546@safari-7618-branch

Source/WebCore/page/Quirks.cpp

@@ -71,6 +71,10 @@
 #include <JavaScriptCore/SourceProvider.h>
 #include <JavaScriptCore/StackVisitor.h>
 
+#if PLATFORM(IOS_FAMILY)
+#include <pal/system/ios/UserInterfaceIdiom.h>
+#endif
+
 #if PLATFORM(COCOA)
 #include <wtf/cocoa/RuntimeApplicationChecksCocoa.h>
 #endif
@@ -424,10 +428,13 @@ bool Quirks::shouldDisableElementFullscreenQuirk() const
     // Twitter.com video embeds have controls that are too tiny and
     // show page behind fullscreen.
     // (Ref: rdar://121473410)
+    // YouTube.com does not provide AirPlay controls in fullscreen
+    // (Ref: rdar://121471373)
     if (!m_shouldDisableElementFullscreen) {
         m_shouldDisableElementFullscreen = isDomain("vimeo.com"_s)
             || isDomain("instagram.com"_s)
-            || isEmbedDomain("twitter.com"_s);
+            || isEmbedDomain("twitter.com"_s)
+            || (PAL::currentUserInterfaceIdiomIsSmallScreen() && (isDomain("youtube.com"_s) || isEmbedDomain("youtube.com"_s)));
     }
 
     return m_shouldDisableElementFullscreen.value();