[presubmit] Enable readability/namespace linter checking.

src/base/platform/platform-macos.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Platform-specific code for MacOS goes here. For the POSIX-compatible
 // parts, the implementation is in platform-posix.cc.
 
 #include <dlfcn.h>
 #include <mach/mach_init.h>
 #include <mach-o/dyld.h>
@@ skipping 231 matching lines @@
 
 bool VirtualMemory::ReleaseRegion(void* address, size_t size) {
   return munmap(address, size) == 0;
 }
 
 
 bool VirtualMemory::HasLazyCommits() {
   return false;
 }
 
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8