Performance: setTextContent should attempt to set TextNode nodeValue where possible (#7005)

(cherry picked from commit 40f6d3eaca)

src/renderers/dom/client/utils/setTextContent.js

@@ -26,6 +26,14 @@ var setInnerHTML = require('setInnerHTML');
  * @internal
  */
 var setTextContent = function(node, text) {
+  if (text) {
+    var firstChild = node.firstChild;
+    
+    if (firstChild && firstChild === node.lastChild && firstChild.nodeType === 3) {
+      firstChild.nodeValue = text;
+      return;
+    }
+  }
   node.textContent = text;
 };