Shuffle & Cleanup Stuff (#3080)

Source/TextKit/ASTextKitEntityAttribute.h

@@ -0,0 +1,30 @@
+//
+//  ASTextKitEntityAttribute.h
+//  AsyncDisplayKit
+//
+//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+
+#import <Foundation/Foundation.h>
+#import <AsyncDisplayKit/ASBaseDefines.h>
+
+/**
+ The object that should be embedded with ASTextKitEntityAttributeName.  Please note that the entity you provide MUST
+ implement a proper hash and isEqual function or your application performance will grind to a halt due to
+ NSMutableAttributedString's usage of a global hash table of all attributes.  This means the entity should NOT be a
+ Foundation Collection (NSArray, NSDictionary, NSSet, etc.) since their hash function is a simple count of the values
+ in the collection, which causes pathological performance problems deep inside NSAttributedString's implementation.
+
+ rdar://19352367
+ */
+AS_SUBCLASSING_RESTRICTED
+@interface ASTextKitEntityAttribute : NSObject
+
+@property (nonatomic, strong, readonly) id<NSObject> entity;
+
+- (instancetype)initWithEntity:(id<NSObject>)entity;
+
+@end