Move SafeBrowsing to the blocking pool via an experiment.

chrome/browser/safe_browsing/safe_browsing_store_file.cc

 // Copyright (c) 2012 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/safe_browsing/safe_browsing_store_file.h"
 
 #include "base/files/file_util.h"
 #include "base/files/scoped_file.h"
 #include "base/md5.h"
 #include "base/metrics/histogram.h"
@@ skipping 536 matching lines @@
 
   int64 size = 0;
   if (!base::GetFileSize(filename, &size))
     return false;
 
   return static_cast<int64>(ftell(file.get())) == size;
 }
 
 }  // namespace
 
-SafeBrowsingStoreFile::SafeBrowsingStoreFile()
-    : chunks_written_(0), empty_(false), corruption_seen_(false) {}
+SafeBrowsingStoreFile::SafeBrowsingStoreFile(
+    scoped_refptr<base::SequencedTaskRunner> task_runner)
+    : task_runner_(task_runner),
+      chunks_written_(0),
+      empty_(false),
+      corruption_seen_(false) {
+}
 
 SafeBrowsingStoreFile::~SafeBrowsingStoreFile() {
   // Thread-checking is disabled in the destructor due to crbug.com/338486.
-  DetachFromThread();
+  task_runner_ = nullptr;
 
   Close();
 }
 
+bool SafeBrowsingStoreFile::CalledOnValidThread() {
+  return !task_runner_ || task_runner_->RunsTasksOnCurrentThread();
+}
+
 bool SafeBrowsingStoreFile::Delete() {
   DCHECK(CalledOnValidThread());
 
   // The database should not be open at this point.  But, just in
   // case, close everything before deleting.
   if (!Close()) {
     NOTREACHED();
     return false;
   }
 
@@ skipping 569 matching lines @@
   // With SQLite support gone, one way to get to this code is if the
   // existing file is a SQLite file.  Make sure the journal file is
   // also removed.
   const base::FilePath journal_filename(
       basename.value() + FILE_PATH_LITERAL("-journal"));
   if (base::PathExists(journal_filename))
     base::DeleteFile(journal_filename, false);
 
   return true;
 }