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

components/safe_browsing_db/BUILD.gn

+# Copyright 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.
+
+group("safe_browsing_db") {
+  deps = [
+    ":prefix_set",
+    ":safe_browsing_db_util",
+  ]
+}
+
+source_set("prefix_set") {
+  sources = [
+    "prefix_set.cc",
+    "prefix_set.h",
+  ]
+  deps = [
+    "//base",
+  ]
+}
+
+source_set("safe_browsing_db_util") {
+  sources = [
+    "safe_browsing_db_util.cc",
+    "safe_browsing_db_util.h",
+  ]
+  deps = [
+    "//base",
+    "//crypto",
+  ]
+}
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "prefix_set_unittest.cc",
+    "safe_browsing_db_util_unittest.cc",
+  ]
+  deps = [
+    ":prefix_set",
+    ":safe_browsing_db_util",
+    "//base",
+    "//testing/gtest",
+  ]
+}