VR: Split off UI code into a library to ease future unit testing.

chrome/browser/android/vr_shell/ui_element_renderer.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 CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENT_RENDERER_H_
+#define CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENT_RENDERER_H_
+
+#include "device/vr/vr_types.h"
+#include "third_party/skia/include/core/SkColor.h"
+
+namespace vr_shell {
+
+// This is the interface offered by VrShell's GL system to UI elements.
+class UiElementRenderer {
+ public:
+  virtual ~UiElementRenderer() {}
+
+  virtual void DrawTexturedQuad(int texture_data_handle,
+                                const vr::Mat4f& view_proj_matrix,
+                                const gfx::RectF& copy_rect,
+                                float opacity) = 0;
+
+  virtual void DrawGradientQuad(const vr::Mat4f& view_proj_matrix,
+                                const SkColor edge_color,
+                                const SkColor center_color,
+                                float opacity) = 0;
+};
+
+}  // namespace vr_shell
+
+#endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENT_RENDERER_H_