Moved zones and zone related stuff in its own directory.

src/handles.h

 // Copyright 2011 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.
 
 #ifndef V8_HANDLES_H_
 #define V8_HANDLES_H_
 
 #include "include/v8.h"
 #include "src/base/functional.h"
 #include "src/base/macros.h"
 #include "src/checks.h"
 #include "src/globals.h"
-#include "src/zone.h"
+#include "src/zone/zone.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class DeferredHandles;
 class HandleScopeImplementer;
 class Isolate;
 class Object;
 
@@ skipping 387 matching lines @@
     next = limit = NULL;
     sealed_level = level = 0;
     canonical_scope = NULL;
   }
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HANDLES_H_