Adding drawable to CRD andorid and iOS gl rendering pipeline.

remoting/client/display/drawable.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef REMOTING_CLIENT_DISPLAY_DRAWABLE_H_
+#define REMOTING_CLIENT_DISPLAY_DRAWABLE_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+
+namespace remoting {
+
+class Canvas;
+
+enum DrawableZIndex {
+  AUTO = -1,
+  DESKTOP = 100,
+  CURSOR_FEEDBACK = 200,
+  CURSOR = 300,
+};
+
+class Drawable {
+ public:
+  Drawable() {}
+  virtual ~Drawable(){};
+
+  // Sets the canvas on which the object will be drawn.
+  // If |canvas| is nullptr, nothing will happen when calling Draw().
+  virtual void SetCanvas(Canvas* canvas) = 0;
+
+  // Draws the object on the canvas.
+  // Return true if you have a next frame.
+  virtual bool Draw() = 0;
+
+  // Used for the renderer to keep a stack of drawables.
+  virtual base::WeakPtr<Drawable> GetWeakPtr() = 0;
+
+  int GetZIndex() { return z_index_; };
+
+  // Specify the Z Index for this drawable. A higher Z Index will draw after a
+  // lower z index. Elements with the same Z Index will draw in order inserted.
+  void SetZIndex(int z_index) { z_index_ = z_index; };
+
+ private:
+  int z_index_ = DrawableZIndex::AUTO;
+
+  DISALLOW_COPY_AND_ASSIGN(Drawable);
+};
+
+namespace drawable {
+
+struct {
+  bool operator()(base::WeakPtr<Drawable> a, base::WeakPtr<Drawable> b) {
+    return a->GetZIndex() < b->GetZIndex();
+  }
+} ZOrderComparator;
+
+}  // namespace drawable
+
+}  // namespace remoting
+
+#endif  // REMOTING_CLIENT_DISPLAY_DRAWABLE_H_