Implement Evaluate without creating new classes.

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 3d6006e57e87431d92579cc158d948b7a5c574bc..ad786e840fa42d7b7fd2943732efbbbdfa680d68 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -1684,6 +1684,7 @@ class Function : public Object {
     }
     switch (kind()) {
       case RawFunction::kRegularFunction:
+      case RawFunction::kEvalFunction:
       case RawFunction::kGetterFunction:
       case RawFunction::kSetterFunction:
       case RawFunction::kImplicitGetter:
@@ -1708,6 +1709,7 @@ class Function : public Object {
     }
     switch (kind()) {
       case RawFunction::kRegularFunction:
+      case RawFunction::kEvalFunction:
       case RawFunction::kGetterFunction:
       case RawFunction::kSetterFunction:
       case RawFunction::kImplicitGetter:
@@ -1962,6 +1964,10 @@ class Function : public Object {
     return kind() == RawFunction::kSignatureFunction;
   }
 
+  bool IsEvalFunction() const {
+    return kind() == RawFunction::kEvalFunction;
+  }
+
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawFunction));
   }
@@ -1984,6 +1990,10 @@ class Function : public Object {
                                          const Function& parent,
                                          intptr_t token_pos);
 
+  static RawFunction* NewEvalFunction(const Class& owner,
+                                      const Script& script,
+                                      bool is_static);
+
   // Creates a new static initializer function which is invoked in the implicit
   // static getter function.
   static RawFunction* NewStaticInitializer(const Field& field);
@@ -2058,6 +2068,8 @@ class Function : public Object {
   void set_implicit_closure_function(const Function& value) const;
   RawInstance* implicit_static_closure() const;
   void set_implicit_static_closure(const Instance& closure) const;
+  RawScript* eval_script() const;
+  void set_eval_script(const Script& value) const;
   void set_num_optional_parameters(intptr_t value) const;  // Encoded value.
   void set_kind_tag(intptr_t value) const;
   void set_data(const Object& value) const;