Hotlist Slow: Remove extra thread pool created by VolumeMountWatcherWin.

BUG=458541

Review URL: https://codereview.chromium.org/974633002

Cr-Commit-Position: refs/heads/master@{#318936}

components/storage_monitor/storage_monitor_win_unittest.cc

@@ -97,7 +97,6 @@ void StorageMonitorWinTest::SetUp() {
 void StorageMonitorWinTest::TearDown() {
   RunUntilIdle();
   monitor_->RemoveObserver(&observer_);
-  volume_mount_watcher_->ShutdownWorkerPool();
 
   // Windows storage monitor must be destroyed on the same thread
   // as construction.

components/storage_monitor/test_volume_mount_watcher_win.cc

@@ -11,6 +11,7 @@
 #include "base/files/scoped_temp_dir.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/storage_monitor/storage_info.h"
+#include "content/public/browser/browser_thread.h"
 
 namespace storage_monitor {
 
@@ -108,7 +109,7 @@ void TestVolumeMountWatcherWin::SetAttachedDevicesFake() {
 }
 
 void TestVolumeMountWatcherWin::FlushWorkerPoolForTesting() {
-  device_info_worker_pool_->FlushForTesting();
+  content::BrowserThread::GetBlockingPool()->FlushForTesting();
 }
 
 void TestVolumeMountWatcherWin::DeviceCheckComplete(
@@ -150,8 +151,4 @@ VolumeMountWatcherWin::GetAttachedDevicesCallbackType
   return base::Bind(&FakeGetSingleAttachedDevice);
 }
 
-void TestVolumeMountWatcherWin::ShutdownWorkerPool() {
-  device_info_worker_pool_->Shutdown();
-}
-
 }  // namespace storage_monitor

components/storage_monitor/test_volume_mount_watcher_win.h

@@ -53,10 +53,6 @@ class TestVolumeMountWatcherWin : public VolumeMountWatcherWin {
   virtual GetDeviceDetailsCallbackType
       GetDeviceDetailsCallback() const override;
 
-  // Should be used by unit tests to make sure the worker pool doesn't survive
-  // into other test runs.
-  void ShutdownWorkerPool();
-
  private:
   std::vector<base::FilePath> devices_checked_;
   scoped_ptr<base::WaitableEvent> device_check_complete_event_;

components/storage_monitor/volume_mount_watcher_win.cc

@@ -34,6 +34,8 @@ namespace {
 
 const DWORD kMaxPathBufLen = MAX_PATH + 1;
 
+const char kDeviceInfoTaskRunnerName[] = "device-info-task-runner";
+
 enum DeviceType {
   FLOPPY,
   REMOVABLE,
@@ -324,18 +326,12 @@ void EjectDeviceInThreadPool(
 
 }  // namespace
 
-const int kWorkerPoolNumThreads = 3;
-const char* kWorkerPoolNamePrefix = "DeviceInfoPool";
-
 VolumeMountWatcherWin::VolumeMountWatcherWin()
-    : device_info_worker_pool_(new base::SequencedWorkerPool(
-          kWorkerPoolNumThreads, kWorkerPoolNamePrefix)),
-      notifications_(NULL),
-      weak_factory_(this) {
-  task_runner_ =
-      device_info_worker_pool_->GetSequencedTaskRunnerWithShutdownBehavior(
-          device_info_worker_pool_->GetSequenceToken(),
-          base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
+    : notifications_(NULL), weak_factory_(this) {
+  base::SequencedWorkerPool* pool = content::BrowserThread::GetBlockingPool();
+  device_info_task_runner_ = pool->GetSequencedTaskRunnerWithShutdownBehavior(
+      pool->GetNamedSequenceToken(kDeviceInfoTaskRunnerName),
+      base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
 }
 
 // static
@@ -361,7 +357,7 @@ void VolumeMountWatcherWin::Init() {
   // so a posted task from the constructor would never run. Therefore, do all
   // the initializations here.
   base::PostTaskAndReplyWithResult(
-      task_runner_.get(), FROM_HERE, GetAttachedDevicesCallback(),
+      device_info_task_runner_.get(), FROM_HERE, GetAttachedDevicesCallback(),
       base::Bind(&VolumeMountWatcherWin::AddDevicesOnUIThread,
                  weak_factory_.GetWeakPtr()));
 }
@@ -374,7 +370,7 @@ void VolumeMountWatcherWin::AddDevicesOnUIThread(
     if (ContainsKey(pending_device_checks_, removable_devices[i]))
       continue;
     pending_device_checks_.insert(removable_devices[i]);
-    task_runner_->PostTask(
+    device_info_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&VolumeMountWatcherWin::RetrieveInfoForDeviceAndAdd,
                    removable_devices[i], GetDeviceDetailsCallback(),
@@ -503,7 +499,6 @@ void VolumeMountWatcherWin::SetNotifications(
 
 VolumeMountWatcherWin::~VolumeMountWatcherWin() {
   weak_factory_.InvalidateWeakPtrs();
-  device_info_worker_pool_->Shutdown();
 }
 
 void VolumeMountWatcherWin::HandleDeviceAttachEventOnUIThread(
@@ -548,9 +543,9 @@ void VolumeMountWatcherWin::EjectDevice(
     return;
   }
 
-  task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&EjectDeviceInThreadPool, device, callback, task_runner_, 0));
+  device_info_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&EjectDeviceInThreadPool, device, callback,
+                            device_info_task_runner_, 0));
 }
 
 }  // namespace storage_monitor

components/storage_monitor/volume_mount_watcher_win.h

@@ -16,7 +16,6 @@
 #include "base/memory/weak_ptr.h"
 #include "base/sequenced_task_runner.h"
 #include "base/strings/string16.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "components/storage_monitor/storage_info.h"
 #include "components/storage_monitor/storage_monitor.h"
 
@@ -90,11 +89,8 @@ class VolumeMountWatcherWin {
   virtual GetAttachedDevicesCallbackType GetAttachedDevicesCallback() const;
   virtual GetDeviceDetailsCallbackType GetDeviceDetailsCallback() const;
 
-  // Worker pool used to collect device information. Used because some
-  // devices freeze workers trying to get device info, resulting in
-  // shutdown hangs.
-  scoped_refptr<base::SequencedWorkerPool> device_info_worker_pool_;
-  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  // Used for device info calls that may take a long time.
+  scoped_refptr<base::SequencedTaskRunner> device_info_task_runner_;
 
  private:
   friend class TestVolumeMountWatcherWin;