Merge the tonic layer from skydart branch back to master

sky/engine/tonic/dart_error.cc

+// 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.
+
+#include "sky/engine/config.h"
+#include "sky/engine/tonic/dart_error.h"
+
+#include "base/logging.h"
+
+namespace blink {
+
+namespace DartError {
+
+const char kInvalidArgument[] = "Invalid argument.";
+
+}  // namespace DartError
+
+bool LogIfError(Dart_Handle handle) {
+  if (Dart_IsError(handle)) {
+    LOG(ERROR) << Dart_GetError(handle);
+    return true;
+  }
+  return false;
+}
+
+}  // namespace blink