Minor code improvements for RCTTextInput

Summary: Expose hasUnseenUpdates in ReactShadowNode. Various text input cleanup and fixes.

Differential Revision: D2975870

fb-gh-sync-id: 26c4c0d36e82aaa025b4760603cc48c47ebf46a3
shipit-source-id: 26c4c0d36e82aaa025b4760603cc48c47ebf46a3

ReactAndroid/src/main/java/com/facebook/react/uimanager/ReactShadowNode.java

@@ -105,6 +105,10 @@ public class ReactShadowNode extends CSSNode {
     }
   }
 
+  public boolean hasUnseenUpdates() {
+    return mNodeUpdated;
+  }
+
   @Override
   protected void dirty() {
     if (!isVirtual()) {