Temorarily comment out NOTREACHED in task manager.

chrome/browser/task_management/providers/child_process_task_provider.cc

 // Copyright 2015 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_management/providers/child_process_task_provider.h"
 
 #include "base/process/process.h"
 #include "base/stl_util.h"
 #include "chrome/browser/task_management/providers/child_process_task.h"
 #include "content/public/browser/browser_child_process_host_iterator.h"
@@ skipping 126 matching lines @@
 }
 
 void ChildProcessTaskProvider::DeleteTask(base::ProcessHandle handle) {
   auto itr = tasks_by_handle_.find(handle);
 
   // The following case should never happen since we start observing
   // |BrowserChildProcessObserver| only after we collect all pre-existing child
   // processes and are notified (on the UI thread) that the collection is
   // completed at |ChildProcessDataCollected()|.
   if (itr == tasks_by_handle_.end()) {
-    NOTREACHED();
+    // BUG(crbug.com/611067): Temporarily removing due to test flakes. The
+    // reason why this happens is well understood (see bug), but there's no
+    // quick and easy fix.
+    // NOTREACHED();
     return;
   }
 
   ChildProcessTask* task = itr->second;
 
   NotifyObserverTaskRemoved(task);
 
   // Finally delete the task.
   tasks_by_handle_.erase(itr);
   tasks_by_pid_.erase(task->process_id());
   delete task;
 }
 
 }  // namespace task_management