Use weak cells in dependent code.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 5ee91913251c81f4833f9230afc419b59f7db384..08dff55cd4dc3d82ceacef06a3fc27d2c6168298 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4720,21 +4720,6 @@ void DependentCode::set_number_of_entries(DependencyGroup group, int value) {
 }
 
 
-bool DependentCode::is_code_at(int i) {
-  return get(kCodesStartIndex + i)->IsCode();
-}
-
-Code* DependentCode::code_at(int i) {
-  return Code::cast(get(kCodesStartIndex + i));
-}
-
-
-CompilationInfo* DependentCode::compilation_info_at(int i) {
-  return reinterpret_cast<CompilationInfo*>(
-      Foreign::cast(get(kCodesStartIndex + i))->foreign_address());
-}
-
-
 void DependentCode::set_object_at(int i, Object* object) {
   set(kCodesStartIndex + i, object);
 }
@@ -4745,11 +4730,6 @@ Object* DependentCode::object_at(int i) {
 }
 
 
-Object** DependentCode::slot_at(int i) {
-  return RawFieldOfElementAt(kCodesStartIndex + i);
-}
-
-
 void DependentCode::clear_at(int i) {
   set_undefined(kCodesStartIndex + i);
 }