[presubmit] Enable readability/namespace linter checking.

src/base/platform/platform-solaris.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 Solaris 10 goes here. For the POSIX-compatible
 // parts, the implementation is in platform-posix.cc.
 
 #ifdef __sparc
 # error "V8 does not support the SPARC CPU architecture."
 #endif
@@ skipping 190 matching lines @@
 bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
   return munmap(base, size) == 0;
 }
 
 
 bool VirtualMemory::HasLazyCommits() {
   // TODO(alph): implement for the platform.
   return false;
 }
 
-} }  // namespace v8::base
+}  // namespace base
+}  // namespace v8