[iOS] Entering fullscreen from iframe without explicit viewport resul…

…ts in badly cropped video

https://bugs.webkit.org/show_bug.cgi?id=270909
rdar://123725878

Reviewed by Eric Carlson.

Follow-up fix to 276138@main: resetViewportDefaultConfiguration() will not trigger viewportDidChange(),
and therefore calling those methods in that order can leave the calculated viewport in an inconsistent state.
Instead, ensure resetViewportDefaultConfiguration() is called before viewportDidChange() by calling
isInFullscreenChanged() before willEnterFullscreen().

* Source/WebKit/WebProcess/FullScreen/WebFullScreenManager.cpp:
(WebKit::WebFullScreenManager::willEnterFullScreen):

Canonical link: https://commits.webkit.org/276427@main

Source/WebKit/WebProcess/FullScreen/WebFullScreenManager.cpp

@@ -319,6 +319,8 @@ void WebFullScreenManager::willEnterFullScreen(WebCore::HTMLMediaElementEnums::V
 
     ALWAYS_LOG(LOGIDENTIFIER, "<", m_element->tagName(), " id=\"", m_element->getIdAttribute(), "\">");
 
+    m_page->isInFullscreenChanged(WebPage::IsInFullscreenMode::Yes);
+
     if (!m_element->document().fullscreenManager().willEnterFullscreen(*m_element, mode)) {
         close();
         return;
@@ -329,8 +331,6 @@ void WebFullScreenManager::willEnterFullScreen(WebCore::HTMLMediaElementEnums::V
         return;
     }
 
-    m_page->isInFullscreenChanged(WebPage::IsInFullscreenMode::Yes);
-
 #if !PLATFORM(IOS_FAMILY)
     m_page->hidePageBanners();
 #endif