Fix fullscreen elements in pinch viewport mode.

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index e87ee438000f7cdccbbd7d5d1b373c83cd69aa19..1f408250578509ebdc55c433317e2c896e92dccf 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -33,6 +33,7 @@
 #include "core/css/FontFaceSet.h"
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/DocumentMarkerController.h"
+#include "core/dom/Fullscreen.h"
 #include "core/editing/FrameSelection.h"
 #include "core/editing/RenderedPosition.h"
 #include "core/events/OverflowEvent.h"
@@ -3861,6 +3862,11 @@ void FrameView::positionScrollbarLayers()
 
 bool FrameView::userInputScrollable(ScrollbarOrientation orientation) const
 {
+    Document* document = frame().document();
+    Element* fullscreenElement = Fullscreen::fullscreenElementFrom(*document);
+    if (fullscreenElement && fullscreenElement != document->documentElement())
+        return false;
+
     ScrollbarMode mode = (orientation == HorizontalScrollbar) ?
         m_horizontalScrollbarMode : m_verticalScrollbarMode;