Remember thread's task when sampling use it when filtering

runtime/vm/profiler_test.cc

Index: runtime/vm/profiler_test.cc
diff --git a/runtime/vm/profiler_test.cc b/runtime/vm/profiler_test.cc
index d923897ba6bac4526814deea40a5b87246056473..e1b28fe9f1590a8c403e1723f92ad916c7487178 100644
--- a/runtime/vm/profiler_test.cc
+++ b/runtime/vm/profiler_test.cc
@@ -201,6 +201,7 @@ class AllocationFilter : public SampleFilter {
                    int64_t time_origin_micros = -1,
                    int64_t time_extent_micros = -1)
       : SampleFilter(isolate,
+                     Thread::kMutatorTask,
                      time_origin_micros,
                      time_extent_micros),
         cid_(cid),
@@ -2308,6 +2309,7 @@ static void InsertFakeSample(SampleBuffer* sample_buffer,
   sample->Init(isolate,
                OS::GetCurrentMonotonicMicros(),
                OSThread::Current()->trace_id());
+  sample->set_thread_task(Thread::kMutatorTask);
 
   intptr_t i = 0;
   while (pc_offsets[i] != 0) {