Check the pipeline ID of the new root layer.

This isn't related to any known issue, but is just to ensure that the IDs are
set correctly within this function.

src/components/main/compositing/compositor.rs

@@ -367,8 +367,10 @@ impl IOCompositor {
             }
             _ => {
                 match self.root_pipeline {
-                    Some(ref root_pipeline) => (root_pipeline.clone(), LayerId::null()),
-                    None => fail!("Compositor: Received new layer without initialized pipeline"),
+                    Some(ref root_pipeline) if root_pipeline.id == id => {
+                        (root_pipeline.clone(), LayerId::null())
+                    },
+                    _ => fail!("Compositor: Received new layer without initialized pipeline"),
                 }
             }
         };