Add intentional optimization comment in Node::setTextContent

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index 8af4165eb24a4b736848148c34141be39e915632..03dfb7da2d718bbc033505b588e97228e1c963d7 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -1515,9 +1515,6 @@ void Node::setTextContent(const String& text)
         case DOCUMENT_FRAGMENT_NODE: {
             // FIXME: Merge this logic into replaceChildrenWithText.
             RefPtrWillBeRawPtr<ContainerNode> container = toContainerNode(this);
-            // No need to do anything if the text is identical.
-            if (container->hasOneTextChild() && toText(container->firstChild())->data() == text)
-                return;
             ChildListMutationScope mutation(*this);
             container->removeChildren();
             // Note: This API will not insert empty text nodes: