Convert USERSELECT_ALL to a runtime enabled feature.

Source/core/dom/Position.cpp

Index: Source/core/dom/Position.cpp
diff --git a/Source/core/dom/Position.cpp b/Source/core/dom/Position.cpp
index c917fb5bf97a64c57766a55d202d19a370c2d1c6..c71c10207ca7cdb3492b8fdc5462e9ea34a2749d 100644
--- a/Source/core/dom/Position.cpp
+++ b/Source/core/dom/Position.cpp
@@ -852,10 +852,9 @@ ContainerNode* Position::findParent(const Node* node)
     return node->parentNode();
 }
 
-#if ENABLE(USERSELECT_ALL)
 bool Position::nodeIsUserSelectAll(const Node* node)
 {
-    return node && node->renderer() && node->renderer()->style()->userSelect() == SELECT_ALL;
+    return RuntimeEnabledFeatures::userSelectAllEnabled() && node && node->renderer() && node->renderer()->style()->userSelect() == SELECT_ALL;
 }
 
 Node* Position::rootUserSelectAllForNode(Node* node)
@@ -879,7 +878,6 @@ Node* Position::rootUserSelectAllForNode(Node* node)
     }
     return candidateRoot;
 }
-#endif
 
 bool Position::isCandidate() const
 {