Removed unused variable to fix Linux build.

TBR=erik.corry@gmail.com
Review URL: http://codereview.chromium.org/115917

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2075 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/execution.cc

@@ -591,7 +591,6 @@ Object* Execution::DebugBreakHelper() {
   // Collect the break state before clearing the flags.
   bool debug_command_only =
       StackGuard::IsDebugCommand() && !StackGuard::IsDebugBreak();
-  bool is_debug_break = StackGuard::IsDebugBreak();
 
   // Clear the debug request flags.
   StackGuard::Continue(DEBUGBREAK);