Merge the tonic layer from skydart branch back to master

sky/engine/tonic/dart_class_library.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_class_library.h"
+
+#include "base/logging.h"
+#include "sky/engine/tonic/dart_wrapper_info.h"
+
+namespace blink {
+
+DartClassLibrary::DartClassLibrary() : provider_(nullptr) {
+}
+
+DartClassLibrary::~DartClassLibrary() {
+  // Note that we don't need to delete these persistent handles because this
+  // object lives as long as the isolate. The handles will get deleted when the
+  // isolate dies.
+}
+
+Dart_PersistentHandle DartClassLibrary::GetClass(const DartWrapperInfo& info) {
+  DCHECK(provider_);
+
+  const auto& result = cache_.add(&info, nullptr);
+  if (!result.isNewEntry)
+    return result.storedValue->value;
+
+  Dart_Handle class_handle = provider_->GetClassByName(info.interface_name);
+  result.storedValue->value = Dart_NewPersistentHandle(class_handle);
+  return result.storedValue->value;
+}
+
+}  // namespace blink