Revert of Straightens outs DEPS in mojo/common

mojo/message_pump/BUILD.gn

Index: mojo/message_pump/BUILD.gn
diff --git a/mojo/message_pump/BUILD.gn b/mojo/message_pump/BUILD.gn
deleted file mode 100644
index df027de029658f65d657bf0af0caa8e00a1cef0b..0000000000000000000000000000000000000000
--- a/mojo/message_pump/BUILD.gn
+++ /dev/null
@@ -1,23 +0,0 @@
-# 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.
-
-import("//testing/test.gni")
-
-source_set("message_pump") {
-  sources = [
-    "handle_watcher.cc",
-    "handle_watcher.h",
-    "message_pump_mojo.cc",
-    "message_pump_mojo.h",
-    "message_pump_mojo_handler.h",
-    "time_helper.cc",
-    "time_helper.h",
-  ]
-
-  deps = [
-    "//base",
-    "//base/third_party/dynamic_annotations",
-    "//third_party/mojo/src/mojo/public/cpp/system",
-  ]
-}