Linux native notifications: Support closing and updating notifications

ui/base/glib/scoped_gobject.h

+// Copyright 2017 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 UI_BASE_GLIB_SCOPED_GOBJECT_H_
+#define UI_BASE_GLIB_SCOPED_GOBJECT_H_
+
+// Similar in spirit to a std::unique_ptr.
+template <typename T>
+class ScopedGObject {
+ public:
+  ScopedGObject() : obj_(nullptr) {}
+
+  explicit ScopedGObject(T* obj) : obj_(obj) { Ref(); }
+
+  ScopedGObject(const ScopedGObject<T>& other) = delete;
+
+  ScopedGObject(ScopedGObject<T>&& other) : obj_(other.obj_) {
+    other.obj_ = nullptr;
+  }
+
+  ~ScopedGObject() { reset(); }
+
+  ScopedGObject<T>& operator=(const ScopedGObject<T>& other) = delete;
+
+  ScopedGObject<T>& operator=(ScopedGObject<T>&& other) {
+    reset();
+    obj_ = other.obj_;
+    other.obj_ = nullptr;
+    return *this;
+  }
+
+  operator T*() { return obj_; }
+
+  void reset(T* obj = nullptr) {
+    Unref();
+    obj_ = obj;
+    Ref();
+  }
+
+ private:
+  void Ref() {
+    // Remove the floating reference from |obj_| if it has one.
+    if (obj_ && g_object_is_floating(obj_))
+      g_object_ref_sink(obj_);
+  }
+
+  // This function is necessary so that libgtkui can overload it in
+  // the case of T = GtkStyleContext.
+  void Unref() {
+    if (obj_)
+      g_object_unref(obj_);
+  }
+
+  T* obj_;
+};
+
+#endif  // UI_BASE_GLIB_SCOPED_GOBJECT_H_