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

src/heap.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 12 matching lines @@
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_HEAP_H_
 #define V8_HEAP_H_
 
 #include "zone-inl.h"
 
-namespace v8 { namespace internal {
+namespace v8 {
+namespace internal {
 
 // Defines all the roots in Heap.
 #define STRONG_ROOT_LIST(V)                             \
   V(Map, meta_map)                                      \
   V(Map, heap_number_map)                               \
   V(Map, short_string_map)                              \
   V(Map, medium_string_map)                             \
   V(Map, long_string_map)                               \
   V(Map, short_ascii_string_map)                        \
   V(Map, medium_ascii_string_map)                       \
@@ skipping 1262 matching lines @@
   int marked_count_;
 
   // The count from the end of the previous full GC.  Will be zero if there
   // was no previous full GC.
   int previous_marked_count_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_