Merge the tonic layer from skydart branch back to master

sky/engine/tonic/dart_state.h

Index: sky/engine/tonic/dart_state.h
diff --git a/sky/engine/tonic/dart_state.h b/sky/engine/tonic/dart_state.h
new file mode 100644
index 0000000000000000000000000000000000000000..88a0b4af86a0ca78bfb6c1356b46e17cf35d1ca9
--- /dev/null
+++ b/sky/engine/tonic/dart_state.h
@@ -0,0 +1,62 @@
+// 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_DART_STATE_H_
+#define SKY_ENGINE_TONIC_DART_STATE_H_
+
+#include "base/logging.h"
+#include "base/memory/weak_ptr.h"
+#include "base/supports_user_data.h"
+#include "dart/runtime/include/dart_api.h"
+#include "sky/engine/wtf/OwnPtr.h"
+#include "sky/engine/wtf/PassRefPtr.h"
+#include "sky/engine/wtf/RefCounted.h"
+
+namespace blink {
+class DartStringCache;
+class DartClassLibrary;
+
+// DartState represents the state associated with a given Dart isolate. The
+// lifetime of this object is controlled by the DartVM. If you want to hold a
+// reference to a DartState instance, please hold a base::WeakPtr<DartState>.
+//
+// DartState is analogous to gin::PerIsolateData and JSC::ExecState.
+class DartState : public base::SupportsUserData {
+ public:
+  class Scope {
+   public:
+    Scope(DartState* dart_state);
+    ~Scope();
+  };
+
+  DartState();
+  virtual ~DartState();
+
+  static DartState* From(Dart_Isolate isolate);
+  static DartState* Current();
+
+  base::WeakPtr<DartState> GetWeakPtr();
+
+  Dart_Isolate isolate() { return isolate_; }
+  void set_isolate(Dart_Isolate isolate) {
+    CHECK(!isolate_);
+    isolate_ = isolate;
+  }
+
+  DartClassLibrary& class_library() { return *class_library_; }
+  DartStringCache& string_cache() { return *string_cache_; }
+
+ private:
+  Dart_Isolate isolate_;
+  OwnPtr<DartClassLibrary> class_library_;
+  OwnPtr<DartStringCache> string_cache_;
+
+  base::WeakPtrFactory<DartState> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(DartState);
+};
+
+}  // namespace blink
+
+#endif  // SKY_ENGINE_TONIC_DART_STATE_H_