Maintain a FixedArray for the optimized code map.

src/debug/debug.cc

Index: src/debug/debug.cc
diff --git a/src/debug/debug.cc b/src/debug/debug.cc
index d6b4ebb62271092029783e50cdad6c6e698ea53c..6e55f13337b877e26921f23b45e427056b100e61 100644
--- a/src/debug/debug.cc
+++ b/src/debug/debug.cc
@@ -1307,7 +1307,7 @@ bool Debug::PrepareFunctionForBreakPoints(Handle<SharedFunctionInfo> shared) {
   {
     SharedFunctionInfo::Iterator iterator(isolate_);
     while (SharedFunctionInfo* shared = iterator.Next()) {
-      if (!shared->optimized_code_map()->IsSmi()) {
+      if (!shared->OptimizedCodeMapIsCleared()) {
         shared->ClearOptimizedCodeMap();
       }
     }