Add experiment to skip waiting until all updates of collection/table view are committed in -accessibilityElements

The wait was introduced in #1217 which blocks the main thread until updates are proccessed. We suspect this causes perf regressions accross the app and need to confirm this via an experiment.

Schemas/configuration.json

@@ -19,10 +19,12 @@
                     "exp_unfair_lock",
                     "exp_infer_layer_defaults",
                     "exp_network_image_queue",
-                    "exp_dealloc_queue_v2",
                     "exp_collection_teardown",
                     "exp_framesetter_cache",
-                    "exp_skip_clear_data"
+                    "exp_skip_clear_data",
+                    "exp_did_enter_preload_skip_asm_layout",
+                    "exp_disable_a11y_cache",
+                    "exp_skip_a11y_wait"
                 ]
     		}
 		}

Source/ASCollectionView.mm

@@ -2455,7 +2455,9 @@ static NSString * const kReuseIdentifier = @"_ASCollectionReuseIdentifier";
 
 - (NSArray *)accessibilityElements
 {
-  [self waitUntilAllUpdatesAreCommitted];
+  if (!ASActivateExperimentalFeature(ASExperimentalSkipAccessibilityWait)) {
+    [self waitUntilAllUpdatesAreCommitted];
+  }
   return [super accessibilityElements];
 }
 

Source/ASExperimentalFeatures.h

@@ -29,6 +29,7 @@ typedef NS_OPTIONS(NSUInteger, ASExperimentalFeatures) {
   ASExperimentalSkipClearData = 1 << 8,                     // exp_skip_clear_data
   ASExperimentalDidEnterPreloadSkipASMLayout = 1 << 9,      // exp_did_enter_preload_skip_asm_layout
   ASExperimentalDisableAccessibilityCache = 1 << 10,        // exp_disable_a11y_cache
+  ASExperimentalSkipAccessibilityWait = 1 << 11,            // exp_skip_a11y_wait
   ASExperimentalFeatureAll = 0xFFFFFFFF
 };
 

Source/ASExperimentalFeatures.mm

@@ -22,7 +22,8 @@ NSArray<NSString *> *ASExperimentalFeaturesGetNames(ASExperimentalFeatures flags
                                       @"exp_framesetter_cache",
                                       @"exp_skip_clear_data",
                                       @"exp_did_enter_preload_skip_asm_layout",
-                                      @"exp_disable_a11y_cache"]));
+                                      @"exp_disable_a11y_cache",
+                                      @"exp_skip_a11y_wait"]));
   
   if (flags == ASExperimentalFeatureAll) {
     return allNames;

Source/ASTableView.mm

@@ -2004,7 +2004,9 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
 
 - (NSArray *)accessibilityElements
 {
-  [self waitUntilAllUpdatesAreCommitted];
+  if (!ASActivateExperimentalFeature(ASExperimentalSkipAccessibilityWait)) {
+    [self waitUntilAllUpdatesAreCommitted];
+  }
   return [super accessibilityElements];
 }
 

Tests/ASConfigurationTests.mm

@@ -28,7 +28,8 @@ static ASExperimentalFeatures features[] = {
   ASExperimentalFramesetterCache,
   ASExperimentalSkipClearData,
   ASExperimentalDidEnterPreloadSkipASMLayout,
-  ASExperimentalDisableAccessibilityCache
+  ASExperimentalDisableAccessibilityCache,
+  ASExperimentalSkipAccessibilityWait,
 };
 
 @interface ASConfigurationTests : ASTestCase <ASConfigurationDelegate>
@@ -51,7 +52,8 @@ static ASExperimentalFeatures features[] = {
     @"exp_framesetter_cache",
     @"exp_skip_clear_data",
     @"exp_did_enter_preload_skip_asm_layout",
-    @"exp_disable_a11y_cache"
+    @"exp_disable_a11y_cache",
+    @"exp_skip_a11y_wait"
   ];
 }