Only set node.value if it's equal to initialValue

In IE11 textContent is populated when the placeholder attribute is set.
Without this check, we end up setting node.value equal to the
placeholder text, causing the textarea to actually render with the text
inside.

This check makes sure that textContent is equal to our expected
initialValue, which should be the case when using defaultValue.

src/renderers/dom/client/wrappers/ReactDOMTextarea.js

@@ -167,9 +167,15 @@ var ReactDOMTextarea = {
     // This is in postMount because we need access to the DOM node, which is not
     // available until after the component has mounted.
     var node = ReactDOMComponentTree.getNodeFromInstance(inst);
-
-    // Warning: node.value may be the empty string at this point (IE11) if placeholder is set.
-    node.value = node.textContent; // Detach value from defaultValue
+    var textContent = node.textContent;
+
+    // Only set node.value if textContent is equal to the expected
+    // initial value. In IE10/IE11 ther eis a bug where the placeholder attribute
+    // will populate textContent as well.
+    // https://developer.microsoft.com/microsoft-edge/platform/issues/101525/
+    if (textContent === inst._wrapperState.initialValue) {
+      node.value = textContent;
+    }
   },
 };