Remove usage of SequencedWorkerPool::GetNamedSequenceToken from ChromeDownloadManagerDelegate.

SequencedWorkerPool is being deprecated in favor of TaskScheduler.

BUG=667892
TBR=hirono@chromium.org, kinuko@chromium.org,

Review-Url: https://codereview.chromium.org/2887933002
Cr-Commit-Position: refs/heads/master@{#473894}

chrome/browser/chromeos/drive/download_handler.cc

@@ -6,6 +6,8 @@
 
 #include <stddef.h>
 
+#include <utility>
+
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/macros.h"
@@ -104,10 +106,10 @@ void MoveDownloadedFile(const base::FilePath& downloaded_file,
 
 // Used to implement CheckForFileExistence().
 void ContinueCheckingForFileExistence(
-    const content::CheckForFileExistenceCallback& callback,
+    content::CheckForFileExistenceCallback callback,
     FileError error,
     std::unique_ptr<ResourceEntry> entry) {
-  callback.Run(error == FILE_ERROR_OK);
+  std::move(callback).Run(error == FILE_ERROR_OK);
 }
 
 // Returns true if |download| is a Drive download created from data persisted
@@ -247,11 +249,11 @@ bool DownloadHandler::IsDriveDownload(const DownloadItem* download) {
 
 void DownloadHandler::CheckForFileExistence(
     const DownloadItem* download,
-    const content::CheckForFileExistenceCallback& callback) {
+    content::CheckForFileExistenceCallback callback) {
   file_system_->GetResourceEntry(
       util::ExtractDrivePath(GetTargetPath(download)),
       base::Bind(&ContinueCheckingForFileExistence,
-                 callback));
+                 base::Passed(std::move(callback))));
 }
 
 void DownloadHandler::SetFreeDiskSpaceDelayForTesting(

chrome/browser/chromeos/drive/download_handler.h

@@ -71,9 +71,8 @@ class DownloadHandler : public AllDownloadItemNotifier::Observer {
   bool IsDriveDownload(const content::DownloadItem* download);
 
   // Checks a file corresponding to the download item exists in Drive.
-  void CheckForFileExistence(
-      const content::DownloadItem* download,
-      const content::CheckForFileExistenceCallback& callback);
+  void CheckForFileExistence(const content::DownloadItem* download,
+                             content::CheckForFileExistenceCallback callback);
 
   // Calculates request space for |downloads|.
   int64_t CalculateRequestSpace(

chrome/browser/download/chrome_download_manager_delegate.cc

@@ -5,6 +5,7 @@
 #include "chrome/browser/download/chrome_download_manager_delegate.h"
 
 #include <string>
+#include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ -17,7 +18,6 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/task_runner.h"
 #include "base/task_scheduler/post_task.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
@@ -212,8 +212,11 @@ ChromeDownloadManagerDelegate::ChromeDownloadManagerDelegate(Profile* profile)
     : profile_(profile),
       next_download_id_(content::DownloadItem::kInvalidId),
       download_prefs_(new DownloadPrefs(profile)),
-      weak_ptr_factory_(this) {
-}
+      check_for_file_existence_task_runner_(
+          base::CreateSequencedTaskRunnerWithTraits(
+              {base::MayBlock(), base::TaskPriority::BACKGROUND,
+               base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN})),
+      weak_ptr_factory_(this) {}
 
 ChromeDownloadManagerDelegate::~ChromeDownloadManagerDelegate() {
   // If a DownloadManager was set for this, Shutdown() must be called.
@@ -533,29 +536,28 @@ void ChromeDownloadManagerDelegate::ShowDownloadInShell(
   platform_util::ShowItemInFolder(profile_, platform_path);
 }
 
+void ContinueCheckingForFileExistence(
+    content::CheckForFileExistenceCallback callback) {
+  std::move(callback).Run(false);
+}
+
 void ChromeDownloadManagerDelegate::CheckForFileExistence(
     DownloadItem* download,
-    const content::CheckForFileExistenceCallback& callback) {
+    content::CheckForFileExistenceCallback callback) {
 #if defined(OS_CHROMEOS)
   drive::DownloadHandler* drive_download_handler =
       drive::DownloadHandler::GetForProfile(profile_);
   if (drive_download_handler &&
       drive_download_handler->IsDriveDownload(download)) {
-    drive_download_handler->CheckForFileExistence(download, callback);
+    drive_download_handler->CheckForFileExistence(download,
+                                                  std::move(callback));
     return;
   }
 #endif
-  static const char kSequenceToken[] = "ChromeDMD-FileExistenceChecker";
-  base::SequencedWorkerPool* worker_pool = BrowserThread::GetBlockingPool();
-  scoped_refptr<base::SequencedTaskRunner> task_runner =
-      worker_pool->GetSequencedTaskRunnerWithShutdownBehavior(
-          worker_pool->GetNamedSequenceToken(kSequenceToken),
-          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
   base::PostTaskAndReplyWithResult(
-      task_runner.get(),
-      FROM_HERE,
-      base::Bind(&base::PathExists, download->GetTargetFilePath()),
-      callback);
+      check_for_file_existence_task_runner_.get(), FROM_HERE,
+      base::BindOnce(&base::PathExists, download->GetTargetFilePath()),
+      std::move(callback));
 }
 
 std::string

chrome/browser/download/chrome_download_manager_delegate.h

@@ -16,6 +16,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "base/sequenced_task_runner.h"
 #include "chrome/browser/download/download_path_reservation_tracker.h"
 #include "chrome/browser/download/download_target_determiner_delegate.h"
 #include "chrome/browser/download/download_target_info.h"
@@ -85,7 +86,7 @@ class ChromeDownloadManagerDelegate
   void ShowDownloadInShell(content::DownloadItem* download) override;
   void CheckForFileExistence(
       content::DownloadItem* download,
-      const content::CheckForFileExistenceCallback& callback) override;
+      content::CheckForFileExistenceCallback callback) override;
   std::string ApplicationClientIdForFileScanning() const override;
 
   // Opens a download using the platform handler. DownloadItem::OpenDownload,
@@ -168,6 +169,12 @@ class ChromeDownloadManagerDelegate
   IdCallbackVector id_callbacks_;
   std::unique_ptr<DownloadPrefs> download_prefs_;
 
+  // SequencedTaskRunner to check for file existence. A sequence is used so that
+  // a large download history doesn't cause a large number of concurrent disk
+  // operations.
+  const scoped_refptr<base::SequencedTaskRunner>
+      check_for_file_existence_task_runner_;
+
 #if BUILDFLAG(ENABLE_EXTENSIONS)
   // Maps from pending extension installations to DownloadItem IDs.
   typedef base::hash_map<extensions::CrxInstaller*,

content/public/browser/download_manager_delegate.h

@@ -64,7 +64,7 @@ using DownloadTargetCallback =
 using DownloadOpenDelayedCallback = base::Callback<void(bool)>;
 
 // Called with the result of CheckForFileExistence().
-using CheckForFileExistenceCallback = base::Callback<void(bool result)>;
+using CheckForFileExistenceCallback = base::OnceCallback<void(bool result)>;
 
 using DownloadIdCallback = base::Callback<void(uint32_t)>;
 
@@ -152,9 +152,8 @@ class CONTENT_EXPORT DownloadManagerDelegate {
   virtual void ShowDownloadInShell(DownloadItem* download) {}
 
   // Checks whether a downloaded file still exists.
-  virtual void CheckForFileExistence(
-      DownloadItem* download,
-      const CheckForFileExistenceCallback& callback) {}
+  virtual void CheckForFileExistence(DownloadItem* download,
+                                     CheckForFileExistenceCallback callback) {}
 
   // Return a GUID string used for identifying the application to the system AV
   // function for scanning downloaded files. If no GUID is provided or if the