Force a11y services to off for complex_layout_semantics_perf test (#108906)

dev/benchmarks/complex_layout/test_driver/semantics_perf_test.dart

@@ -15,6 +15,21 @@ void main() {
     late FlutterDriver driver;
 
     setUpAll(() async {
+      // Turn off any accessibility services that may be running. The purpose of
+      // the test is to measure the time it takes to create the initial
+      // semantics tree in isolation. If accessibility services are on, the
+      // semantics tree gets generated during the first frame and we can't
+      // measure it in isolation.
+      final Process run = await Process.start(_adbPath(), const <String>[
+        'shell',
+        'settings',
+        'put',
+        'secure',
+        'enabled_accessibility_services',
+        'null',
+      ]);
+      await run.exitCode;
+
       driver = await FlutterDriver.connect(printCommunication: true);
     });
 
@@ -31,7 +46,13 @@ void main() {
       await driver.forceGC();
 
       final Timeline timeline = await driver.traceAction(() async {
-        expect(await driver.setSemantics(true), isTrue);
+        expect(
+          await driver.setSemantics(true),
+          isTrue,
+          reason: 'Could not toggle semantics to on because semantics were already '
+                  'on, but the test needs to toggle semantics to measure the initial '
+                  'semantics tree generation in isolation.'
+        );
       });
 
       final Iterable<TimelineEvent>? semanticsEvents = timeline.events?.where((TimelineEvent event) => event.name == 'SEMANTICS');
@@ -45,3 +66,12 @@ void main() {
     }, timeout: Timeout.none);
   });
 }
+
+String _adbPath() {
+  final String? androidHome = Platform.environment['ANDROID_HOME'] ?? Platform.environment['ANDROID_SDK_ROOT'];
+  if (androidHome == null) {
+    return 'adb';
+  } else {
+    return p.join(androidHome, 'platform-tools', 'adb');
+  }
+}