Fix Custom Drawable Layer usage of private headers (#2039)

platform/darwin/app/ExampleCustomDrawableStyleLayer.h

@@ -1,11 +1,6 @@
 #import "Mapbox.h"
 
-#import "MLNFoundation.h"
-#import "MLNStyleValue.h"
-#import "MLNStyleLayer.h"
-#import "MLNGeometry.h"
-
-@interface ExampleCustomDrawableStyleLayer : MLNStyleLayer
+@interface ExampleCustomDrawableStyleLayer : MLNCustomDrawableStyleLayer
 
 - (instancetype)initWithIdentifier:(NSString *)identifier;
 

platform/darwin/app/ExampleCustomDrawableStyleLayer.mm

@@ -1,10 +1,6 @@
 #import "ExampleCustomDrawableStyleLayer.h"
 #import "MLNStyleLayer.h"
-
-#import "MLNCustomDrawableStyleLayer_Private.h"
-#import "MLNStyle_Private.h"
-#import "MLNStyleLayer_Private.h"
-#import "MLNGeometry_Private.h"
+#import "MLNCustomDrawableStyleLayer.h"
 
 #include <mbgl/layermanager/layer_factory.hpp>
 #include <mbgl/style/layer.hpp>

platform/darwin/src/MLNCustomDrawableStyleLayer.h

@@ -1,10 +1,19 @@
+#import <Foundation/Foundation.h>
+
+#import "MLNFoundation.h"
 #import "MLNFoundation.h"
 #import "MLNStyleValue.h"
 #import "MLNStyleLayer.h"
 #import "MLNGeometry.h"
 
+#ifdef __cplusplus
+#include <mbgl/style/layer.hpp>
+#endif
+
 @interface MLNCustomDrawableStyleLayer : MLNStyleLayer
 
-- (instancetype)initWithIdentifier:(NSString *)identifier;
+#ifdef __cplusplus
+- (instancetype)initWithPendingLayer:(std::unique_ptr<mbgl::style::Layer>)pendingLayer;
+#endif
 
 @end

platform/darwin/src/MLNCustomDrawableStyleLayer.mm

@@ -14,18 +14,12 @@
 
 @implementation MLNCustomDrawableStyleLayer
 
-/// @note
-/// Inherit MLNCustomDrawableStyleLayer class and override initWithIdentifier method to create and attach a valid CustomDrawableLayerHost instance
-/// Example:
-/// - (instancetype)initWithIdentifier:(NSString *)identifier {
-///    auto layer = std::make_unique<mbgl::style::CustomDrawableLayer>(identifier.UTF8String,
-///                                                            std::make_unique<ExampleCustomDrawableStyleLayerHost>(self));
-///    return self = [super initWithPendingLayer:std::move(layer)];
-/// }
-///
-- (instancetype)initWithIdentifier:(NSString *)identifier {
-    auto layer = std::make_unique<mbgl::style::CustomDrawableLayer>(identifier.UTF8String, nullptr);
-    return self = [super initWithPendingLayer:std::move(layer)];
+- (instancetype)initWithRawLayer:(mbgl::style::Layer *)rawLayer {
+    return [super initWithRawLayer:rawLayer];
+}
+
+- (instancetype)initWithPendingLayer:(std::unique_ptr<mbgl::style::Layer>)pendingLayer {
+    return [super initWithPendingLayer:std::move(pendingLayer)];
 }
 
 @end