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;
+
+// Interface for drawing on a Canvas from a renderer.
+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(base::WeakPtr<Canvas> canvas) = 0;
+
+  // Draws the object on the canvas.
+  // Returns true if there is a pending next frame.
+  virtual bool Draw() = 0;
+
+  // Used for the renderer to keep a stack of drawables.
+  virtual base::WeakPtr<Drawable> GetWeakPtr() = 0;
+
+  // ZIndexDefault is a recommendation for Z Index of drawable components.
+  enum ZIndexDefault {

[Sergey Ulanov, 2017/01/11 22:47:31]

I'm not sure we need 'Default' part of the name - it doesn't really add
anything.

[nicholss, 2017/01/11 23:43:25]

Done.

+    DESKTOP = 100,
+    CURSOR_FEEDBACK = 200,
+    CURSOR = 300,
+  };
+
+  // A higher Z Index shiould be draw ontop of a lower z index. Elements with
+  // the

[Sergey Ulanov, 2017/01/11 22:47:31]

nit: comment formatting

[nicholss, 2017/01/11 23:43:25]

some magic from git cl format.

+  // same Z Index should draw in order inserted into the renderer.
+  virtual int ZIndex() = 0;

[Sergey Ulanov, 2017/01/11 22:47:31]

GetZIndex()

[nicholss, 2017/01/11 23:43:25]

Done.

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Drawable);
+};
+
+}  // namespace remoting
+
+#endif  // REMOTING_CLIENT_DISPLAY_DRAWABLE_H_