Implement external strings.

runtime/vm/object_store.cc

Index: runtime/vm/object_store.cc
diff --git a/runtime/vm/object_store.cc b/runtime/vm/object_store.cc
index 4f14b88e7f577f433504fe6bcf2ea0a39cf28e02..6a5e7c9eb25499ef531e3c5b8029a9e5dd097e3f 100644
--- a/runtime/vm/object_store.cc
+++ b/runtime/vm/object_store.cc
@@ -25,11 +25,15 @@ ObjectStore::ObjectStore()
     one_byte_string_class_(Class::null()),
     two_byte_string_class_(Class::null()),
     four_byte_string_class_(Class::null()),
+    external_one_byte_string_class_(Class::null()),
+    external_two_byte_string_class_(Class::null()),
+    external_four_byte_string_class_(Class::null()),
     bool_interface_(Type::null()),
     bool_class_(Class::null()),
     list_interface_(Type::null()),
     array_class_(Class::null()),
     immutable_array_class_(Class::null()),
+    byte_buffer_class_(Class::null()),
     unhandled_exception_class_(Class::null()),
     stacktrace_class_(Class::null()),
     jsregexp_class_(Class::null()),
@@ -75,6 +79,9 @@ RawClass* ObjectStore::GetClass(int index) {
     case kOneByteStringClass: return one_byte_string_class_;
     case kTwoByteStringClass: return two_byte_string_class_;
     case kFourByteStringClass: return four_byte_string_class_;
+    case kExternalOneByteStringClass: return external_one_byte_string_class_;
+    case kExternalTwoByteStringClass: return external_two_byte_string_class_;
+    case kExternalFourByteStringClass: return external_four_byte_string_class_;
     case kBoolClass: return bool_class_;
     case kArrayClass: return array_class_;
     case kImmutableArrayClass: return immutable_array_class_;
@@ -107,6 +114,12 @@ int ObjectStore::GetClassIndex(const RawClass* raw_class) {
     return kTwoByteStringClass;
   } else if (raw_class == four_byte_string_class_) {
     return kFourByteStringClass;
+  } else if (raw_class == external_one_byte_string_class_) {
+    return kExternalOneByteStringClass;
+  } else if (raw_class == external_two_byte_string_class_) {
+    return kExternalTwoByteStringClass;
+  } else if (raw_class == external_four_byte_string_class_) {
+    return kExternalFourByteStringClass;
   } else if (raw_class == bool_class_) {
     return kBoolClass;
   } else if (raw_class == array_class_) {