Fix a race in the EmbedderA11yTest.A11yTreeIsConsistent tests

Author: jason-simmons

shell/platform/embedder/tests/embedder_a11y_unittests.cc

@@ -160,12 +160,12 @@ TEST_F(EmbedderA11yTest, A11yTreeIsConsistent) {
     auto handle = Dart_GetNativeBooleanArgument(args, 0, &enabled);
     ASSERT_FALSE(Dart_IsError(handle));
     ASSERT_TRUE(enabled);
-    latch.Signal();
+    notify_features_latch.Signal();
   };
   result = FlutterEngineUpdateAccessibilityFeatures(
       engine.get(), kFlutterAccessibilityFeatureReduceMotion);
   ASSERT_EQ(result, FlutterEngineResult::kSuccess);
-  latch.Wait();
+  notify_features_latch.Wait();
 
   // Wait for UpdateSemantics callback on platform (current) thread.
   latch.Wait();
@@ -350,12 +350,12 @@ TEST_F(EmbedderA11yTest, A11yTreeIsConsistentUsingLegacyCallbacks) {
     auto handle = Dart_GetNativeBooleanArgument(args, 0, &enabled);
     ASSERT_FALSE(Dart_IsError(handle));
     ASSERT_TRUE(enabled);
-    latch.Signal();
+    notify_features_latch.Signal();
   };
   result = FlutterEngineUpdateAccessibilityFeatures(
       engine.get(), kFlutterAccessibilityFeatureReduceMotion);
   ASSERT_EQ(result, FlutterEngineResult::kSuccess);
-  latch.Wait();
+  notify_features_latch.Wait();
 
   // Wait for UpdateSemantics callback on platform (current) thread.
   latch.Wait();