[core] Adjust layer source properties to better reflect reality

* Layer source ID is immutable; must be provided to the constructor
* Layer source layer is mutable
* Layers with GeoJSON sources do not have a source layer

While here, make Layer::copy impl-private.

1 files changed, 0 insertions, 8 deletions

diff --git a/src/mbgl/style/layer.cpp b/src/mbgl/style/layer.cpp
index 342699a2c9..6eff64ae09 100644
--- a/src/mbgl/style/layer.cpp
+++ b/src/mbgl/style/layer.cpp
@@ -38,13 +38,5 @@ void Layer::setMaxZoom(float maxZoom) const {
     baseImpl->maxZoom = maxZoom;
 }
 
-std::unique_ptr<Layer> Layer::copy(const std::string& id,
-                                   const std::string& ref) const {
-    std::unique_ptr<Layer> result = baseImpl->clone();
-    result->baseImpl->id = id;
-    result->baseImpl->ref = ref;
-    return result;
-}
-
 } // namespace style
 } // namespace mbgl