Strawman: check strong mode free variables against the global object.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index cf6d1613e6545724162d07b7fa22e4ab759f58c6..2c4f3ddb45cd3cd5c588555646966c7ee22119ac 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4306,6 +4306,8 @@ class ScopeInfo : public FixedArray {
   // exposed to the user in a debugger.
   bool LocalIsSynthetic(int var);
 
+  String* StrongModeFreeVariableName(int var);
+
   // Lookup support for serialized scope info. Returns the
   // the stack slot index for a given slot name if the slot is
   // present; otherwise returns a value < 0. The name must be an internalized
@@ -4358,11 +4360,12 @@ class ScopeInfo : public FixedArray {
   // 3. The number of non-parameter variables allocated on the stack.
   // 4. The number of non-parameter and parameter variables allocated in the
   //    context.
-#define FOR_EACH_NUMERIC_FIELD(V)          \
-  V(Flags)                                 \
-  V(ParameterCount)                        \
-  V(StackLocalCount)                       \
-  V(ContextLocalCount)
+#define FOR_EACH_NUMERIC_FIELD(V) \
+  V(Flags)                        \
+  V(ParameterCount)               \
+  V(StackLocalCount)              \
+  V(ContextLocalCount)            \
+  V(StrongModeFreeVariableCount)
 
 #define FIELD_ACCESSORS(name)                            \
   void Set##name(int value) {                            \
@@ -4414,10 +4417,12 @@ class ScopeInfo : public FixedArray {
   //    information about the function variable. It always occupies two array
   //    slots:  a. The name of the function variable.
   //            b. The context or stack slot index for the variable.
+  // FIXME: update the comment
   int ParameterEntriesIndex();
   int StackLocalEntriesIndex();
   int ContextLocalNameEntriesIndex();
   int ContextLocalInfoEntriesIndex();
+  int StrongModeFreeVariableEntriesIndex();
   int FunctionNameEntryIndex();
 
   // Location of the function variable for named function expressions.