Add ASExperimentalSkipClearData #trivial (TextureGroup#1136)

* Add ASExperimentalSkipClearData

* Move the experiment check within the if clause

Author: maicki

Source/ASCollectionView.mm

@@ -576,7 +576,8 @@ - (void)setAsyncDelegate:(id<ASCollectionDelegate>)asyncDelegate
 - (void)_asyncDelegateOrDataSourceDidChange
 {
   ASDisplayNodeAssertMainThread();
-  if (_asyncDataSource == nil && _asyncDelegate == nil) {
+  
+  if (_asyncDataSource == nil && _asyncDelegate == nil && !ASActivateExperimentalFeature(ASExperimentalSkipClearData)) {
     [_dataController clearData];
   }
 }

Source/ASExperimentalFeatures.h

@@ -24,6 +24,7 @@ typedef NS_OPTIONS(NSUInteger, ASExperimentalFeatures) {
   ASExperimentalDeallocQueue = 1 << 6,                      // exp_dealloc_queue_v2
   ASExperimentalCollectionTeardown = 1 << 7,                // exp_collection_teardown
   ASExperimentalFramesetterCache = 1 << 8,                  // exp_framesetter_cache
+  ASExperimentalSkipClearData = 1 << 9,                     // exp_skip_clear_data
   ASExperimentalFeatureAll = 0xFFFFFFFF
 };
 

Source/ASExperimentalFeatures.m

@@ -20,7 +20,8 @@
                                       @"exp_network_image_queue",
                                       @"exp_dealloc_queue_v2",
                                       @"exp_collection_teardown",
-                                      @"exp_framesetter_cache"]));
+                                      @"exp_framesetter_cache"
+                                      @"exp_skip_clear_data"]));
 
   if (flags == ASExperimentalFeatureAll) {
     return allNames;