Fix compilation with debuggersupport=off.

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 309 matching lines @@
     thread_data_table_ = new Isolate::ThreadDataTable();
     default_isolate_ = new Isolate();
   }
   // Can't use SetIsolateThreadLocals(default_isolate_, NULL) here
   // becase a non-null thread data may be already set.
   Thread::SetThreadLocal(isolate_key_, default_isolate_);
   CHECK(default_isolate_->PreInit());
 }
 
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
 Debugger* Isolate::GetDefaultIsolateDebugger() {
   EnsureDefaultIsolate();
   return default_isolate_->debugger();
 }
+#endif
 
 
 StackGuard* Isolate::GetDefaultIsolateStackGuard() {
   EnsureDefaultIsolate();
   return default_isolate_->stack_guard();
 }
 
 
 void Isolate::EnterDefaultIsolate() {
   EnsureDefaultIsolate();
@@ skipping 561 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