Merge commit '7621e2f8dec938cf48181c8b10afc9b01f444e68' into beta

submodules/Display/Source/GridItem.swift

@@ -0,0 +1,39 @@
+import Foundation
+import UIKit
+import AsyncDisplayKit
+
+public protocol GridSection {
+    var height: CGFloat { get }
+    var hashValue: Int { get }
+    
+    func isEqual(to: GridSection) -> Bool
+    func node() -> ASDisplayNode
+}
+
+public protocol GridItem {
+    var section: GridSection? { get }
+    func node(layout: GridNodeLayout, synchronousLoad: Bool) -> GridItemNode
+    func update(node: GridItemNode)
+    var aspectRatio: CGFloat { get }
+    var fillsRowWithHeight: (CGFloat, Bool)? { get }
+    var fillsRowWithDynamicHeight: ((CGFloat) -> CGFloat)? { get }
+    var customItemSize: CGSize? { get }
+}
+
+public extension GridItem {
+    var aspectRatio: CGFloat {
+        return 1.0
+    }
+    
+    var fillsRowWithHeight: (CGFloat, Bool)? {
+        return nil
+    }
+    
+    var fillsRowWithDynamicHeight: ((CGFloat) -> CGFloat)? {
+        return nil
+    }
+    
+    var customItemSize: CGSize? {
+        return nil
+    }
+}