[core] Split LayerPlacementData and BucketPlacementData

src/mbgl/renderer/layers/render_symbol_layer.cpp

@@ -589,7 +589,7 @@ void RenderSymbolLayer::prepare(const LayerPrepareParameters& params) {
                 placementData.push_back({*bucket, renderTile, featureIndex, nullopt});
             } else {
                 for (const auto& sortKeyRange : bucket->sortKeyRanges) {
-                    LayerPlacementData layerData{*bucket, renderTile, featureIndex, sortKeyRange};
+                    BucketPlacementData layerData{*bucket, renderTile, featureIndex, sortKeyRange};
                     auto sortPosition = std::upper_bound(
                         placementData.cbegin(), placementData.cend(), layerData, [](const auto& lhs, const auto& rhs) {
                             assert(lhs.sortKeyRange && rhs.sortKeyRange);

src/mbgl/renderer/render_layer.hpp

@@ -36,7 +36,7 @@ public:
     size_t end;
 };
 
-class LayerPlacementData {
+class BucketPlacementData {
 public:
     std::reference_wrapper<Bucket> bucket;
     std::reference_wrapper<const RenderTile> tile;
@@ -44,6 +44,8 @@ public:
     optional<SortKeyRange> sortKeyRange;
 };
 
+using LayerPlacementData = std::list<BucketPlacementData>;
+
 class LayerPrepareParameters {
 public:
     RenderSource* source;
@@ -105,7 +107,7 @@ public:
 
     virtual void prepare(const LayerPrepareParameters&);
 
-    const std::list<LayerPlacementData>& getPlacementData() const { return placementData; }
+    const LayerPlacementData& getPlacementData() const { return placementData; }
 
     // Latest evaluated properties.
     Immutable<style::LayerProperties> evaluatedProperties;
@@ -134,7 +136,7 @@ protected:
     // evaluated StyleProperties object and is updated accordingly.
     RenderPass passes = RenderPass::None;
 
-    std::list<LayerPlacementData> placementData;
+    LayerPlacementData placementData;
 
 private:
     // Some layers may not render correctly on some hardware when the vertex attribute limit of