Avoid "using namespace blink" in global scope

third_party/WebKit/Source/core/editing/BUILD.gn

 # Copyright 2016 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("//third_party/WebKit/Source/core/core.gni")
 
 blink_core_sources("editing") {
   split_count = 5
   sources = [
     "CaretDisplayItemClient.cpp",
@@ skipping 269 matching lines @@
     "state_machines/StateMachineUtil.cpp",
     "state_machines/StateMachineUtil.h",
     "state_machines/TextSegmentationMachineState.cpp",
     "state_machines/TextSegmentationMachineState.h",
   ]
 
   if (is_mac) {
     sources += [ "commands/SmartReplaceCF.cpp" ]
   }
 
-  if (is_mac) {
-    jumbo_excluded_sources = [
-      # Using "using blink" in global scope.
-      "WebSubstringUtil.mm",
-    ]
-  }
-
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "CompositionUnderlineTest.cpp",
@@ skipping 69 matching lines @@
     "//third_party/WebKit/Source:config",
     "//third_party/WebKit/Source:inside_blink",
   ]
 
   deps = [
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/WebKit/Source/core:core",
   ]
 }