Add ENABLE_DEBUGGER_SUPPORT macro....

src/execution.cc

Index: src/execution.cc
===================================================================
--- src/execution.cc	(revision 1738)
+++ src/execution.cc	(working copy)
@@ -305,6 +305,7 @@
 }
 
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
 bool StackGuard::IsDebugBreak() {
   ExecutionAccess access;
   return thread_local_.interrupt_flags_ & DEBUGBREAK;
@@ -331,8 +332,8 @@
     set_limits(kInterruptLimit, access);
   }
 }
+#endif
 
-
 void StackGuard::Continue(InterruptFlag after_what) {
   ExecutionAccess access;
   thread_local_.interrupt_flags_ &= ~static_cast<int>(after_what);
@@ -539,6 +540,7 @@
 
   ContextSwitcher::PreemptionReceived();
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
   if (Debug::InDebugger()) {
     // If currently in the debugger don't do any actual preemption but record
     // that preemption occoured while in the debugger.
@@ -548,11 +550,17 @@
     v8::Unlocker unlocker;
     Thread::YieldCPU();
   }
+#else
+  // Perform preemption.
+  v8::Unlocker unlocker;
+  Thread::YieldCPU();
+#endif
 
   return Heap::undefined_value();
 }
 
 
+#ifdef ENABLE_DEBUGGER_SUPPORT
 Object* Execution::DebugBreakHelper() {
   // Just continue if breaks are disabled.
   if (Debug::disable_break()) {
@@ -598,12 +606,14 @@
   // Return to continue execution.
   return Heap::undefined_value();
 }
+#endif
 
-
 Object* Execution::HandleStackGuardInterrupt() {
+#ifdef ENABLE_DEBUGGER_SUPPORT
   if (StackGuard::IsDebugBreak() || StackGuard::IsDebugCommand()) {
     DebugBreakHelper();
   }
+#endif
   if (StackGuard::IsPreempted()) RuntimePreempt();
   if (StackGuard::IsInterrupted()) {
     // interrupt