Fix an issue that subtitle is not shown for native fullscreen video that is inside an iframe

Source/core/rendering/compositing/GraphicsLayerUpdater.cpp

Index: Source/core/rendering/compositing/GraphicsLayerUpdater.cpp
diff --git a/Source/core/rendering/compositing/GraphicsLayerUpdater.cpp b/Source/core/rendering/compositing/GraphicsLayerUpdater.cpp
index 40c419947199076cd33c2a73106ab36d3df34799..15dc1a365d86916e806e92b3bf52f2f7a46b4f43 100644
--- a/Source/core/rendering/compositing/GraphicsLayerUpdater.cpp
+++ b/Source/core/rendering/compositing/GraphicsLayerUpdater.cpp
@@ -27,6 +27,7 @@
 #include "config.h"
 #include "core/rendering/compositing/GraphicsLayerUpdater.h"
 
+#include "core/html/HTMLMediaElement.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderLayerReflectionInfo.h"
 #include "core/rendering/RenderPart.h"
@@ -37,6 +38,16 @@
 
 namespace WebCore {
 
+bool shouldAppendLayer(const RenderLayer& layer)
+{
+    if (!RuntimeEnabledFeatures::overlayFullscreenVideoEnabled())
+        return true;
+    Node* node = layer.renderer()->node();
+    if (isHTMLMediaElement(*node) && toHTMLMediaElement(node)->isFullscreen())
+        return false;
+    return true;
+}
+
 GraphicsLayerUpdater::GraphicsLayerUpdater(RenderView& renderView)
     : m_renderView(renderView)
     , m_pixelsWithoutPromotingAllTransitions(0.0)
@@ -122,7 +133,8 @@ void GraphicsLayerUpdater::rebuildTree(RenderLayer& layer, Vector<GraphicsLayer*
             }
         }
 
-        childLayersOfEnclosingLayer.append(currentCompositedLayerMapping->childForSuperlayers());
+        if (shouldAppendLayer(layer))
+            childLayersOfEnclosingLayer.append(currentCompositedLayerMapping->childForSuperlayers());
     }
 
     if (!depth) {