Add a Display and ContextProvider concept to mojom, use to recreate

examples/sample_app/spinning_cube.h

Index: examples/sample_app/spinning_cube.h
diff --git a/examples/sample_app/spinning_cube.h b/examples/sample_app/spinning_cube.h
index 757daf64f523fbaf1fba9a7ab9eab91bbc586c87..e52f0ebf11fda05fae96210b1feb2f895d677e06 100644
--- a/examples/sample_app/spinning_cube.h
+++ b/examples/sample_app/spinning_cube.h
@@ -16,13 +16,17 @@ class SpinningCube {
   SpinningCube();
   ~SpinningCube();
 
-  void Init(uint32_t width, uint32_t height);
+  void Init();
   void set_direction(int direction) { direction_ = direction; }
   void set_color(float r, float g, float b) {
     color_[0] = r;
     color_[1] = g;
     color_[2] = b;
   }
+  void set_size(uint32_t width, uint32_t height) {
+    width_ = width;
+    height_ = height;
+  }
   void SetFlingMultiplier(float drag_distance, float drag_time);
   void UpdateForTimeDelta(float delta_time);
   void UpdateForDragDistance(float distance);