Split nested namespaces declaration in two lines in accordance with C++ Style Guide.

src/register-allocator.cc

Index: src/register-allocator.cc
diff --git a/src/register-allocator.cc b/src/register-allocator.cc
index d6f850e3776805064a1267df092fffca52702f25..a3939cbb8e6ee599e16f44cc19ab4fc735ae06b1 100644
--- a/src/register-allocator.cc
+++ b/src/register-allocator.cc
@@ -30,7 +30,8 @@
 #include "codegen-inl.h"
 #include "register-allocator-inl.h"
 
-namespace v8 { namespace internal {
+namespace v8 {
+namespace internal {
 
 // -------------------------------------------------------------------------
 // Result implementation.