Move prefix_set and parts of s_b_util into a new component safe_browsing_db.

components/safe_browsing_db/safe_browsing_db_util.cc

Index: components/safe_browsing_db/safe_browsing_db_util.cc
diff --git a/components/safe_browsing_db/safe_browsing_db_util.cc b/components/safe_browsing_db/safe_browsing_db_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..623bfb3c8386d19a8f9c04d0242d27fbc2d12e3c
--- /dev/null
+++ b/components/safe_browsing_db/safe_browsing_db_util.cc
@@ -0,0 +1,13 @@
+// Copyright (c) 2015 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 "components/safe_browsing_db/safe_browsing_db_util.h"
+
+#include "crypto/sha2.h"
+
+SBFullHash SBFullHashForString(const base::StringPiece& str) {
+  SBFullHash h;
+  crypto::SHA256HashString(str, &h.full_hash, sizeof(h.full_hash));
+  return h;
+}