Allow FlatShadowNode mouting to its own view

Summary: @public This diff adds a `FlatShadowNode.forceMountToView()` method that will render its contents in it own `View`.

Reviewed By: sriramramani

Differential Revision: D2564502

ReactAndroid/src/main/java/com/facebook/react/flat/DrawView.java

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.flat;
+
+import android.graphics.Canvas;
+
+/* package */ final class DrawView implements DrawCommand {
+
+  /* package */ static DrawView INSTANCE = new DrawView();
+
+  private DrawView() {}
+
+  @Override
+  public void draw(FlatViewGroup parent, Canvas canvas) {
+    parent.drawNextChild(canvas);
+  }
+}