Disallow fullscreen from within <frame>, even with allowfullscreen

Source/core/dom/FullscreenElementStack.cpp

Index: Source/core/dom/FullscreenElementStack.cpp
diff --git a/Source/core/dom/FullscreenElementStack.cpp b/Source/core/dom/FullscreenElementStack.cpp
index 239fe6a6a818725700a660821d6efb5922a8b9b2..f4380de31883e5d89a49795557a0b42f7d5fb779 100644
--- a/Source/core/dom/FullscreenElementStack.cpp
+++ b/Source/core/dom/FullscreenElementStack.cpp
@@ -50,6 +50,8 @@ static bool fullscreenIsAllowedForAllOwners(const Document& document)
     if (!owner)
         return true;
     do {
+        if (!isHTMLIFrameElement(owner))
+            return false;
         if (!owner->hasAttribute(allowfullscreenAttr)) {
             if (owner->hasAttribute(webkitallowfullscreenAttr))
                 UseCounter::count(document, UseCounter::PrefixedAllowFullscreenAttribute);