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 6349a0b490e5e4f0e8ea9d25e6f58b963edc911e..dfaacedfc40d34179e3ee90c54b989f209d94c35 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;
 }