Substantially improve behavior of nested Table & Collection Nodes

This ensures memory cleanup happens correctly and introduces a new test project
to support developing new features while stressing tough use cases for correctness.

examples/VerticalWithinHorizontalScrolling/Sample/ViewController.m

@@ -0,0 +1,100 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+#import <AsyncDisplayKit/ASAssert.h>
+
+#import "ViewController.h"
+#import "GradientTableNode.h"
+
+@interface ViewController () <ASCollectionViewDataSource, ASCollectionViewDelegate>
+{
+  ASCollectionView *_pagerView;
+}
+
+@end
+
+@implementation ViewController
+
+#pragma mark -
+#pragma mark UIViewController.
+
+- (instancetype)init
+{
+  if (!(self = [super init]))
+    return nil;
+
+  UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
+  flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
+//  flowLayout.itemSize = [[UIScreen mainScreen] bounds].size;
+  flowLayout.minimumInteritemSpacing = 0;
+  flowLayout.minimumLineSpacing = 0;
+  
+  _pagerView = [[ASCollectionView alloc] initWithCollectionViewLayout:flowLayout];
+  
+  ASRangeTuningParameters rangeTuningParameters;
+  rangeTuningParameters.leadingBufferScreenfuls = 1.0;
+  rangeTuningParameters.trailingBufferScreenfuls = 1.0;
+  [_pagerView setTuningParameters:rangeTuningParameters forRangeType:ASLayoutRangeTypeRender];
+  
+  _pagerView.pagingEnabled = YES;
+  _pagerView.asyncDataSource = self;
+  _pagerView.asyncDelegate = self;
+  
+  self.title = @"Paging Table Nodes";
+  self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRedo
+                                                                                         target:self
+                                                                                         action:@selector(reloadEverything)];
+
+  return self;
+}
+
+- (void)reloadEverything
+{
+  [_pagerView reloadData];
+}
+
+- (void)viewDidLoad
+{
+  [super viewDidLoad];
+
+  [self.view addSubview:_pagerView];
+}
+
+- (void)viewWillLayoutSubviews
+{
+  _pagerView.frame = self.view.bounds;
+  _pagerView.contentInset = UIEdgeInsetsZero;
+}
+
+- (BOOL)prefersStatusBarHidden
+{
+  return YES;
+}
+
+#pragma mark -
+#pragma mark ASTableView.
+
+- (ASCellNode *)collectionView:(ASCollectionView *)collectionView nodeForItemAtIndexPath:(NSIndexPath *)indexPath;
+{
+  CGSize boundsSize = collectionView.bounds.size;
+  CGSize gradientRowSize = CGSizeMake(boundsSize.width, 100);
+  GradientTableNode *node = [[GradientTableNode alloc] initWithElementSize:gradientRowSize];
+  node.preferredFrameSize = boundsSize;
+  return node;
+}
+
+- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
+{
+  return (section == 0 ? 10 : 0);
+}
+
+@end