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/DrawTextLayout.java

@@ -0,0 +1,42 @@
+/**
+ * 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;
+import android.text.Layout;
+
+/**
+ * DrawTextLayout is a DrawCommand that draw {@link Layout}.
+ */
+/* package */ final class DrawTextLayout extends AbstractDrawCommand {
+
+  private Layout mLayout;
+
+  /* package */ DrawTextLayout(Layout layout) {
+    mLayout = layout;
+  }
+
+  /**
+   * Assigns a new {@link Layout} to draw.
+   */
+  public void setLayout(Layout layout) {
+    mLayout = layout;
+  }
+
+  @Override
+  public void draw(Canvas canvas) {
+    float left = getLeft();
+    float top = getTop();
+
+    canvas.translate(left, top);
+    mLayout.draw(canvas);
+    canvas.translate(-left, -top);
+  }
+}