[gardening] Lower threshold for number of trace events in flaky/time-sensitive test

Issue dart-lang/sdk#43713

Change-Id: I6884d08ff08e0e44efcb14b009d9289dba8909ce
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/168021
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Tess Strickland <sstrickl@google.com>
Auto-Submit: Martin Kustermann <kustermann@google.com>

Author: mkustermann

runtime/observatory/tests/service/get_cpu_profile_timeline_rpc_test.dart

@@ -38,7 +38,7 @@ Future checkTimeline(VM vm) async {
   }
 
   List events = result['traceEvents'];
-  expect(events.length, greaterThan(10), reason: "Should have many samples");
+  expect(events.length, greaterThan(0), reason: "Should have samples");
   for (Map event in events) {
     expect(event['ph'], equals('P'));
     expect(event['pid'], isInt);

runtime/observatory_2/tests/service_2/get_cpu_profile_timeline_rpc_test.dart

@@ -38,7 +38,7 @@ Future checkTimeline(VM vm) async {
   }
 
   List events = result['traceEvents'];
-  expect(events.length, greaterThan(10), reason: "Should have many samples");
+  expect(events.length, greaterThan(0), reason: "Should have samples");
   for (Map event in events) {
     expect(event['ph'], equals('P'));
     expect(event['pid'], isInt);