Capture accessibility hierarchy and package it for the sonar plugin

Summary: In this diff we load and call a private API enabling voiceover hierarchy and pass it over via existing channel when client is in the accessibility mode

Reviewed By: lblasa

Differential Revision: D49393813

fbshipit-source-id: 437af1131547218cd52f4a56797707411787d7cf

iOS/Plugins/FlipperKitUIDebuggerPlugin/FlipperKitUIDebuggerPlugin/Observer/UIDTreeObserver.m

@@ -8,6 +8,7 @@
 #if FB_SONARKIT_ENABLED
 
 #import "UIDTreeObserver.h"
+#import "UIDAllyTraversal.h"
 #import "UIDContext.h"
 #import "UIDHierarchyTraversal.h"
 #import "UIDTimeUtilities.h"
@@ -39,15 +40,29 @@
 
   uint64_t t0 = UIDPerformanceNow();
 
-  UIDHierarchyTraversal* traversal = [UIDHierarchyTraversal
-      createWithDescriptorRegister:context.descriptorRegister];
-
   UIDNodeDescriptor* descriptor =
       [context.descriptorRegister descriptorForClass:[node class]];
   UIDNodeDescriptor* rootDescriptor = [context.descriptorRegister
       descriptorForClass:[context.application class]];
 
-  NSArray* nodes = [traversal traverse:node];
+  NSArray* nodes;
+  switch (_traversalMode) {
+    case UIDTraversalModeViewHierarchy: {
+      UIDHierarchyTraversal* const traversal = [UIDHierarchyTraversal
+          createWithDescriptorRegister:context.descriptorRegister];
+      nodes = [traversal traverse:node];
+      break;
+    }
+    case UIDTraversalModeAccessibilityHierarchy: {
+      UIDAllyTraversal* allyTraversal = [[UIDAllyTraversal alloc]
+          initWithDescriptorRegister:context.descriptorRegister];
+      nodes = [allyTraversal traverse:context.application root:node];
+      break;
+    }
+    default:
+      // Unexpected value, abort
+      return;
+  }
 
   uint64_t t1 = UIDPerformanceNow();