[tracing] Fix HostDiscardable dump provider to register on the right thread

content/common/host_discardable_shared_memory_manager.cc

 // Copyright 2014 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 "content/common/host_discardable_shared_memory_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 159 matching lines @@
                      base::Unretained(this)))),
       // Current thread might not have a task runner in tests.
       enforce_memory_policy_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       enforce_memory_policy_pending_(false),
       weak_ptr_factory_(this) {
   DCHECK_NE(memory_limit_, 0u);
   enforce_memory_policy_callback_ =
       base::Bind(&HostDiscardableSharedMemoryManager::EnforceMemoryPolicy,
                  weak_ptr_factory_.GetWeakPtr());
   base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
-      this, "HostDiscardableSharedMemoryManager", nullptr);
+      this, "HostDiscardableSharedMemoryManager",
+      base::ThreadTaskRunnerHandle::Get());
 }
 
 HostDiscardableSharedMemoryManager::~HostDiscardableSharedMemoryManager() {
   base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
       this);
 }
 
 HostDiscardableSharedMemoryManager*
 HostDiscardableSharedMemoryManager::current() {
   return g_discardable_shared_memory_manager.Pointer();
@@ skipping 358 matching lines @@
     return;
 
   enforce_memory_policy_pending_ = true;
   DCHECK(enforce_memory_policy_task_runner_);
   enforce_memory_policy_task_runner_->PostDelayedTask(
       FROM_HERE, enforce_memory_policy_callback_,
       base::TimeDelta::FromMilliseconds(kEnforceMemoryPolicyDelayMs));
 }
 
 }  // namespace content