Fix memory leaks in ~Zone and ~Isolate

src/isolate.cc

 // Copyright 2011 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 1573 matching lines @@
   delete string_tracker_;
   string_tracker_ = NULL;
 
   delete memory_allocator_;
   memory_allocator_ = NULL;
   delete code_range_;
   code_range_ = NULL;
   delete global_handles_;
   global_handles_ = NULL;
 
+  if (external_reference_table_ != NULL) {

[Vitaly Repeshko, 2011/08/16 17:52:32]

It's safe to delete NULL. "if" is not necessary.

[Jakob Kummerow, 2011/08/17 08:47:30]

Done.

+    delete external_reference_table_;
+    external_reference_table_ = NULL;
+  }
+
 #ifdef ENABLE_DEBUGGER_SUPPORT
   delete debugger_;
   debugger_ = NULL;
   delete debug_;
   debug_ = NULL;
 #endif
 }
 
 
 void Isolate::InitializeThreadLocal() {
@@ skipping 261 matching lines @@
 
 #ifdef DEBUG
 #define ISOLATE_FIELD_OFFSET(type, name, ignored)                       \
 const intptr_t Isolate::name##_debug_offset_ = OFFSET_OF(Isolate, name##_);
 ISOLATE_INIT_LIST(ISOLATE_FIELD_OFFSET)
 ISOLATE_INIT_ARRAY_LIST(ISOLATE_FIELD_OFFSET)
 #undef ISOLATE_FIELD_OFFSET
 #endif
 
 } }  // namespace v8::internal