Don't copy Int8Arrays when passing them in as lists of bytes and don't

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/dart.h"
@@ skipping 1932 matching lines @@
   return Api::NewError("Invalid length passed in to access array elements");   \
 
 
 DART_EXPORT Dart_Handle Dart_ListGetAsBytes(Dart_Handle list,
                                             intptr_t offset,
                                             uint8_t* native_array,
                                             intptr_t length) {
   Isolate* isolate = Isolate::Current();
   DARTSCOPE(isolate);
   const Object& obj = Object::Handle(isolate, Api::UnwrapHandle(list));
-  if (obj.IsUint8Array() || obj.IsExternalUint8Array()) {
+  if (obj.IsUint8Array() || obj.IsExternalUint8Array() ||
+      obj.IsInt8Array() || obj.IsExternalInt8Array()) {
     const ByteArray& byte_array = ByteArray::Cast(obj);
     if (Utils::RangeCheck(offset, length, byte_array.Length())) {
       ByteArray::Copy(native_array, byte_array, offset, length);
       return Api::Success(isolate);
     }
     return Api::NewError("Invalid length passed in to access list elements");
   } else if (obj.IsArray()) {
     GET_LIST_ELEMENT_AS_BYTES(isolate,
                               Array,
                               obj,
@@ skipping 2480 matching lines @@
   }
   {
     NoGCScope no_gc;
     RawObject* raw_obj = obj.raw();
     isolate->heap()->SetPeer(raw_obj, peer);
   }
   return Api::Success(isolate);
 }
 
 }  // namespace dart