Revert of Deletes mojo::Callback

mojo/public/cpp/bindings/tests/BUILD.gn

 # 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.
 
 import("../../../mojo_application.gni")
 
 source_set("tests") {
   testonly = true
 
   sources = [
@@ skipping 29 matching lines @@
     "type_conversion_unittest.cc",
     "union_unittest.cc",
     "validation_context_unittest.cc",
     "validation_unittest.cc",
     "variant_test_util.h",
   ]
 
   deps = [
     ":mojo_public_bindings_test_utils",
     "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/bindings:callback",
     "//mojo/public/cpp/system",
     "//mojo/public/cpp/test_support:test_utils",
     "//mojo/public/interfaces/bindings/tests:test_associated_interfaces",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//mojo/public/interfaces/bindings/tests:test_interfaces_experimental",
     "//mojo/public/interfaces/bindings/tests:test_struct_traits_interfaces",
     "//testing/gtest",
   ]
 
   data = [
@@ skipping 22 matching lines @@
       "container_test_util.h",
       "map_common_test.h",
       "variant_test_util.h",
       "wtf_array_unittest.cc",
       "wtf_map_unittest.cc",
       "wtf_types_unittest.cc",
     ]
 
     deps = [
       "//mojo/public/cpp/bindings",
+      "//mojo/public/cpp/bindings:callback",
       "//mojo/public/cpp/system",
       "//mojo/public/interfaces/bindings/tests:test_interfaces",
       "//mojo/public/interfaces/bindings/tests:test_wtf_types",
       "//mojo/public/interfaces/bindings/tests:test_wtf_types_blink",
       "//testing/gtest",
     ]
   }
 }
 
 source_set("struct_with_traits_impl") {
@@ skipping 16 matching lines @@
   ]
 
   if (!is_ios) {
     sources += [ "e2e_perftest.cc" ]
   }
 
   deps = [
     "//base/test:test_support",
     "//mojo/edk/test:test_support",
     "//mojo/public/cpp/bindings",
+    "//mojo/public/cpp/bindings:callback",
     "//mojo/public/cpp/system",
     "//mojo/public/cpp/test_support:test_utils",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//testing/gtest",
   ]
 }
 
 source_set("mojo_public_bindings_test_utils") {
   sources = [
     "validation_test_input_parser.cc",
     "validation_test_input_parser.h",
   ]
 
   deps = [
     "//mojo/public/c/system",
   ]
 }