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;

[gab, 2015/02/19 14:38:23]

No need to do this, just have a commented out:

// DCHECK(task_runner_->RunsTasksOnCurrentThread());

with the same comment above.

The reason this was like this before is that the DCHECK was made in the parent
NonThreadSafe class' destructor.

[Alexei Svitkine (slow), 2015/02/20 15:42:44]

The issue is that Close() has that check.

 
   Close();
 }
 
+bool SafeBrowsingStoreFile::CalledOnValidThread() {
+  return !task_runner_ || task_runner_->RunsTasksOnCurrentThread();

[gab, 2015/02/19 14:38:23]

You can get rid of this I think and just inline

DCHECK(task_runner_->RunsTasksOnCurrentThread());

everywhere I think given the above suggestion.

[Alexei Svitkine (slow), 2015/02/20 15:42:44]

I prefer keeping it a separate method, which doesn't add any overhead in
official builds (since its only called from inside DCHECKs and the unused method
will be stripped out by the linker) while making the checks both more readable
(i.e. don't need to read impl. details of how the check is done) and more easily
updatable if this is part of the code is refactored again.

+}
+
 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;
 }