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

sky/engine/core/painting/Float32List.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_CORE_PAINTING_FLOAT32LIST_H_
+#define SKY_ENGINE_CORE_PAINTING_FLOAT32LIST_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 {

[abarth-chromium, 2015/06/04 16:58:16]

This class should be in //sky/engine/tonic.  It's very general.

[Matt Perry, 2015/06/04 17:22:44]

Done.

+ public:
+  float* data;
+  intptr_t num_elements;
+
+  ~Float32List();

[abarth-chromium, 2015/06/04 16:58:16]

We should have a Float32List constructor that initializes |data| and
|num_elements| to zero.

[Matt Perry, 2015/06/04 17:22:44]

Done.

+
+  void Init(Dart_Handle list);
+
+ private:
+  Dart_Handle dart_handle_;
+};
+
+template <>
+struct DartConverter<Float32List> {
+  static Float32List FromArgumentsWithNullCheck(Dart_NativeArguments args,
+                                                int index,
+                                                Dart_Handle& exception);
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_PAINTING_FLOAT32LIST_H_