re-enable the post_backdrop_filter test with CPU/GPU measurements (#65201)

dev/benchmarks/macrobenchmarks/test_driver/post_backdrop_filter_perf_test.dart

@@ -11,7 +11,7 @@ void main() {
   macroPerfTest(
     'post_backdrop_filter_perf',
     kPostBackdropFilterRouteName,
-    pageDelay: const Duration(seconds: 1),
+    pageDelay: const Duration(seconds: 2),
     duration: const Duration(seconds: 10),
     setupOps: (FlutterDriver driver) async {
       final SerializableFinder backdropFilterCheckbox = find.byValueKey('bdf-checkbox');
@@ -22,7 +22,7 @@ void main() {
 
       final SerializableFinder animateButton = find.byValueKey('bdf-animate');
       await driver.tap(animateButton);
-      await Future<void>.delayed(const Duration(milliseconds: 1000)); // Now animate
+      await Future<void>.delayed(const Duration(milliseconds: 10000)); // Now animate
     },
   );
 }

dev/devicelab/manifest.yaml

@@ -542,11 +542,12 @@ tasks:
     stage: devicelab_ios
     required_agent_capabilities: ["mac/ios"]
 
-  # post_backdrop_filter_perf_ios__timeline_summary:
-  #   description: >
-  #     Measures the runtime performance of animations after a backdrop filter is removed on iOS.
-  #   stage: devicelab_ios
-  #   required_agent_capabilities: ["mac/iphonexs"]
+  post_backdrop_filter_perf_ios__timeline_summary:
+    description: >
+      Measures the runtime performance of animations after a backdrop filter is removed on iOS.
+    stage: devicelab_ios
+    required_agent_capabilities: ["mac/ios"]
+    flaky: true
 
   complex_layout_scroll_perf_ios__timeline_summary:
     description: >