Two TaskManager tests are flaky on debug due to a DCHECK in SharedSampler

chrome/browser/task_manager/sampling/shared_sampler_win.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/task_manager/sampling/shared_sampler.h"
 
 #include <windows.h>
 #include <winternl.h>
 
 #include <algorithm>
@@ skipping 338 matching lines @@
     return;
 
   callbacks_map_.erase(process_id);
 
   if (callbacks_map_.empty())
     ClearState();
 }
 
 void SharedSampler::Refresh(base::ProcessId process_id, int64_t refresh_flags) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-  DCHECK(callbacks_map_.find(process_id) != callbacks_map_.end());
   DCHECK_NE(0, refresh_flags & GetSupportedFlags());
 
   if (process_id == 0)
     return;
 
+  DCHECK(callbacks_map_.find(process_id) != callbacks_map_.end());
+
   if (refresh_flags_ == 0) {
     base::PostTaskAndReplyWithResult(
         blocking_pool_runner_.get(), FROM_HERE,
         base::Bind(&SharedSampler::RefreshOnWorkerThread, this),
         base::Bind(&SharedSampler::OnRefreshDone, this));
   } else {
     // A group of consecutive Refresh calls should all specify the same refresh
     // flags.
     DCHECK_EQ(refresh_flags, refresh_flags_);
   }
@@ skipping 252 matching lines @@
       callback_entry.second.on_physical_memory.Run(physical_bytes);
     }
   }
 
   // Reset refresh_results_ to trigger RefreshOnWorkerThread next time Refresh
   // is called.
   refresh_flags_ = 0;
 }
 
 }  // namespace task_manager