Move SafeBrowsing to the blocking pool via an experiment.

chrome/browser/safe_browsing/safe_browsing_store_file.cc

Index: chrome/browser/safe_browsing/safe_browsing_store_file.cc
diff --git a/chrome/browser/safe_browsing/safe_browsing_store_file.cc b/chrome/browser/safe_browsing/safe_browsing_store_file.cc
index 47c3f9efafd73e8fb954b0a5130230f3fd2f2b0b..358ecf684e754b115dff07d7d37cd4b24e91b264 100644
--- a/chrome/browser/safe_browsing/safe_browsing_store_file.cc
+++ b/chrome/browser/safe_browsing/safe_browsing_store_file.cc
@@ -554,16 +554,25 @@ bool ReadDbStateHelper(const base::FilePath& filename,
 
 }  // 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());