Move TransportSecurityPersister completely to IO thread.

chrome/browser/transport_security_persister.h

Index: chrome/browser/transport_security_persister.h
diff --git a/chrome/browser/transport_security_persister.h b/chrome/browser/transport_security_persister.h
index 96bde66f1e135a7adfb69bb24492ee48781f370b..402aad0f1df0f3bb14ee04d1dd3b53fa880e5243 100644
--- a/chrome/browser/transport_security_persister.h
+++ b/chrome/browser/transport_security_persister.h
@@ -44,7 +44,7 @@
 
 class TransportSecurityPersister
     : public base::RefCountedThreadSafe<TransportSecurityPersister,
-                                        BrowserThread::DeleteOnUIThread>,
+                                        BrowserThread::DeleteOnIOThread>,
       public net::TransportSecurityState::Delegate,
       public ImportantFileWriter::DataSerializer {
  public:
@@ -63,7 +63,7 @@ class TransportSecurityPersister
   virtual bool SerializeData(std::string* data);
 
  private:
-  friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
+  friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>;
   friend class DeleteTask<TransportSecurityPersister>;
 
   virtual ~TransportSecurityPersister();