Use a different map to distinguish eval contexts

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index 6ee1d4c27ea5dfaa708689b38ba00352c64e2d86..c75d07f637ed18933da60bbb1474d134a596b629 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -2599,7 +2599,7 @@ void FastNewClosureStub::GenerateAssembly(CodeStubAssembler* assembler) const {
 // static
 compiler::Node* FastNewFunctionContextStub::Generate(
     CodeStubAssembler* assembler, compiler::Node* function,
-    compiler::Node* slots, compiler::Node* context) {
+    compiler::Node* slots, compiler::Node* context, bool for_eval) {
   typedef compiler::Node Node;
 
   Node* min_context_slots =
@@ -2613,9 +2613,10 @@ compiler::Node* FastNewFunctionContextStub::Generate(
   Node* function_context = assembler->Allocate(size);
 
   Isolate* isolate = assembler->isolate();
-  assembler->StoreMapNoWriteBarrier(
-      function_context,
-      assembler->HeapConstant(isolate->factory()->function_context_map()));
+  Handle<Map> map = for_eval ? isolate->factory()->eval_context_map()
+                             : isolate->factory()->function_context_map();
+  assembler->StoreMapNoWriteBarrier(function_context,
+                                    assembler->HeapConstant(map));
   assembler->StoreObjectFieldNoWriteBarrier(function_context,
                                             Context::kLengthOffset,
                                             assembler->SmiFromWord32(length));
@@ -2656,7 +2657,7 @@ void FastNewFunctionContextStub::GenerateAssembly(
   Node* slots = assembler->Parameter(FastNewFunctionContextDescriptor::kSlots);
   Node* context = assembler->Parameter(Descriptor::kContext);
 
-  assembler->Return(Generate(assembler, function, slots, context));
+  assembler->Return(Generate(assembler, function, slots, context, for_eval()));
 }
 
 // static