Add support for RCTText under FlatUIImplementation

Summary: @public Initial version of FlatUIImplementation lacks any primitives support (such as RCTText, RCTImageView or RCTView). This diff add the first part, RCTText (alongside with RCTVirtualText and RCTRawText).

Reviewed By: sriramramani

Differential Revision: D2693348

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

@@ -0,0 +1,46 @@
+/**
+ * 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.content.Context;
+import android.graphics.Canvas;
+import android.view.ViewGroup;
+
+/**
+ * A view that FlatShadowNode hierarchy maps to. Performs drawing by iterating over
+ * array of DrawCommands, executing them one by one.
+ */
+/* package */ final class FlatViewGroup extends ViewGroup {
+
+  private DrawCommand[] mDrawCommands = DrawCommand.EMPTY_ARRAY;
+
+  /* package */ FlatViewGroup(Context context) {
+    super(context);
+  }
+
+  @Override
+  public void dispatchDraw(Canvas canvas) {
+    super.dispatchDraw(canvas);
+
+    for (DrawCommand drawCommand : mDrawCommands) {
+      drawCommand.draw(canvas);
+    }
+  }
+
+  @Override
+  protected void onLayout(boolean changed, int l, int t, int r, int b) {
+    // nothing to do here
+  }
+
+  /* package */ void mountDrawCommands(DrawCommand[] drawCommands) {
+    mDrawCommands = drawCommands;
+    invalidate();
+  }
+}