components: Add GN build files for three more components.

components/leveldb_proto/BUILD.gn

Index: components/leveldb_proto/BUILD.gn
diff --git a/components/leveldb_proto/BUILD.gn b/components/leveldb_proto/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..9743af0315f2accebcbf22d45f831b04a6f04f8c
--- /dev/null
+++ b/components/leveldb_proto/BUILD.gn
@@ -0,0 +1,28 @@
+# Copyright 2014 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.
+
+source_set("leveldb_proto") {
+  sources = [
+    "leveldb_database.cc",
+    "leveldb_database.h",
+    "proto_database.h",
+    "proto_database_impl.h",
+  ]
+
+  deps = [
+    "//base",
+    "//third_party/leveldatabase",
+  ]
+}
+
+source_set("test_support") {
+  sources = [
+    "testing/fake_db.h",
+  ]
+
+  deps = [
+    ":leveldb_proto",
+    "//components/leveldb_proto/testing/proto",
+  ]
+}