Canvas.concat takes a 16-element Float32List instead of an array.

sky/engine/tonic/float32_list.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SKY_ENGINE_TONIC_FLOAT32_LIST_H_
+#define SKY_ENGINE_TONIC_FLOAT32_LIST_H_
+
+#include "dart/runtime/include/dart_api.h"
+#include "sky/engine/tonic/dart_converter.h"
+
+namespace blink {
+
+// A simple wrapper around a Dart Float32List. It uses Dart_TypedDataAcquireData
+// to obtain a raw pointer to the data, which is released when this object is
+// destroyed.
+//
+// This is designed to be used with DartConverter only.
+class Float32List {
+ public:
+  explicit Float32List(Dart_Handle list);
+  Float32List(Float32List&& other);
+  ~Float32List();
+
+  const float* data() const { return data_; }
+  intptr_t num_elements() const { return num_elements_; }
+
+ private:
+  float* data_;
+  intptr_t num_elements_;
+  Dart_Handle dart_handle_;
+
+  Float32List(const Float32List& other) = delete;
+};
+
+template <>
+struct DartConverter<Float32List> {
+  static Float32List FromArgumentsWithNullCheck(Dart_NativeArguments args,
+                                                int index,
+                                                Dart_Handle& exception);
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_TONIC_FLOAT32_LIST_H_