Support subtitles for native fullscreen video

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index 587f75a98ac8f32f11b912fdcb8cdb1a1c4dcc17..631c40a46288f35fa8f0f353a8de509552c2bdd7 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -66,7 +66,9 @@
 #include "core/platform/NotImplemented.h"
 #include "core/platform/graphics/InbandTextTrackPrivate.h"
 #include "core/platform/graphics/MediaPlayer.h"
+#include "core/rendering/RenderLayerCompositor.h"
 #include "core/rendering/RenderVideo.h"
+#include "core/rendering/RenderView.h"
 #include "modules/mediastream/MediaStreamRegistry.h"
 #include "public/platform/Platform.h"
 #include "weborigin/SecurityOrigin.h"
@@ -3561,12 +3563,16 @@ void HTMLMediaElement::didBecomeFullscreenElement()
 {
     if (hasMediaControls())
         mediaControls()->enteredFullscreen();
+    if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && isVideo())
+        document().renderView()->compositor()->setCompositingLayersNeedRebuild(true);
 }
 
 void HTMLMediaElement::willStopBeingFullscreenElement()
 {
     if (hasMediaControls())
         mediaControls()->exitedFullscreen();
+    if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && isVideo())
+        document().renderView()->compositor()->setCompositingLayersNeedRebuild(true);
 }
 
 WebKit::WebLayer* HTMLMediaElement::platformLayer() const