Chain camera-related systems

Fixes random Changed<Viewport> misses after d5a7330

Author: rmsc

crates/bevy_render/src/lib.rs

@@ -12,7 +12,7 @@ pub mod shader;
 pub mod surface;
 pub mod texture;
 
-use bevy_ecs::{IntoExclusiveSystem, IntoSystem, SystemStage};
+use bevy_ecs::{IntoChainSystem, IntoExclusiveSystem, IntoSystem, SystemStage};
 use bevy_reflect::RegisterTypeBuilder;
 use draw::Visible;
 pub use once_cell;
@@ -141,24 +141,13 @@ impl Plugin for RenderPlugin {
         )
         .add_system_to_stage(
             bevy_app::stage::POST_UPDATE,
-            surface::viewport_system.system(),
-        )
-        .add_system_to_stage(
-            bevy_app::stage::POST_UPDATE,
-            camera::active_cameras_system.system(),
-        )
-        .add_system_to_stage(
-            bevy_app::stage::POST_UPDATE,
-            camera::camera_system::<OrthographicProjection>.system(),
-        )
-        .add_system_to_stage(
-            bevy_app::stage::POST_UPDATE,
-            camera::camera_system::<PerspectiveProjection>.system(),
-        )
-        // registration order matters here. this must come after all camera_system::<T> systems
-        .add_system_to_stage(
-            bevy_app::stage::POST_UPDATE,
-            camera::visible_entities_system.system(),
+            surface::viewport_system
+                .system()
+                .chain(camera::active_cameras_system.system())
+                .chain(camera::camera_system::<OrthographicProjection>.system())
+                .chain(camera::camera_system::<PerspectiveProjection>.system())
+                // registration order matters here. this must come after all camera_system::<T> systems
+                .chain(camera::visible_entities_system.system()),
         )
         .add_system_to_stage(
             stage::RENDER_RESOURCE,