Remove the webkitallowfullscreen content attribute

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 cdee89472c55a09a96684eb1ceef9efa67de884c..d153ed3d1dd4a2d29b7c9fa328098d5d350f7cf1 100644
--- a/Source/core/dom/FullscreenElementStack.cpp
+++ b/Source/core/dom/FullscreenElementStack.cpp
@@ -52,12 +52,8 @@ static bool fullscreenIsAllowedForAllOwners(const Document& document)
     do {
         if (!isHTMLIFrameElement(owner))
             return false;
-        if (!owner->hasAttribute(allowfullscreenAttr)) {
-            if (owner->hasAttribute(webkitallowfullscreenAttr))
-                UseCounter::count(document, UseCounter::PrefixedAllowFullscreenAttribute);
-            else
-                return false;
-        }
+        if (!owner->hasAttribute(allowfullscreenAttr))
+            return false;
     } while ((owner = owner->document().ownerElement()));
     return true;
 }