Avoid reporting frame/raster times for large image changer (#88454)

dev/devicelab/bin/tasks/large_image_changer_perf_ios.dart

@@ -15,5 +15,16 @@ Future<void> main() async {
     'large_image_changer',
     measureCpuGpu: true,
     measureMemory: true,
+    // This benchmark doesn't care about frame times, frame times will be heavily
+    // impacted by IO time for loading the image initially.
+    benchmarkScoreKeys: <String>[
+      'average_cpu_usage',
+      'average_gpu_usage',
+      'average_memory_usage',
+      '90th_percentile_memory_usage',
+      '99th_percentile_memory_usage',
+      'new_gen_gc_count',
+      'old_gen_gc_count',
+    ],
   ).run);
 }