Remove webkitIsFullScreen everywhere except in bindings

Source/web/FullscreenController.cpp

Index: Source/web/FullscreenController.cpp
diff --git a/Source/web/FullscreenController.cpp b/Source/web/FullscreenController.cpp
index 7987d3fa471cc573031f0302a1154cd463e37df3..7b1ccd960727dceb1bac33fe023cfe477df894d1 100644
--- a/Source/web/FullscreenController.cpp
+++ b/Source/web/FullscreenController.cpp
@@ -134,7 +134,7 @@ void FullscreenController::didExitFullScreen()
 
     if (Document* doc = m_fullScreenFrame->document()) {
         if (Fullscreen* fullscreen = Fullscreen::fromIfExists(*doc)) {
-            if (fullscreen->webkitIsFullScreen()) {
+            if (fullscreen->webkitCurrentFullScreenElement()) {
                 if (m_exitFullscreenPageScaleFactor) {
                     m_webViewImpl->setPageScaleFactor(m_exitFullscreenPageScaleFactor);
                     m_webViewImpl->setMainFrameScrollOffset(IntPoint(m_exitFullscreenScrollOffset));