ASDataController improvements

- _populateFromDataSourceWithSectionIndexSet doesn't accept a mutanle array but allocate one itself.
- Remove _populateFromEntireDataSourceWithMutableContexts.
- ASIndexedNodeContext executes its block, nil out the block and return the result.

AsyncDisplayKit/Details/ASIndexedNodeContext.h

@@ -7,11 +7,9 @@
 //
 
 #import <AsyncDisplayKit/ASDataController.h>
-#import <AsyncDisplayKit/ASDimension.h>
 
 @interface ASIndexedNodeContext : NSObject
 
-@property (nonatomic, readonly, strong) ASCellNodeBlock nodeBlock;
 @property (nonatomic, readonly, strong) NSIndexPath *indexPath;
 @property (nonatomic, readonly, assign) ASSizeRange constrainedSize;
 
@@ -19,4 +17,9 @@
                         indexPath:(NSIndexPath *)indexPath
                   constrainedSize:(ASSizeRange)constrainedSize;
 
+/**
+ * Returns a node allocated by executing node block. Node block will be nil out immediately.
+ */
+- (ASCellNode *)allocateNode;
+
 @end