Adds ImmersiveContext and ImmersiveHandlerFactory

ash/shared/immersive_context.cc

Index: ash/shared/immersive_context.cc
diff --git a/ash/shared/immersive_context.cc b/ash/shared/immersive_context.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ab226126890fab228222e4e8d263d90320527a1a
--- /dev/null
+++ b/ash/shared/immersive_context.cc
@@ -0,0 +1,24 @@
+// Copyright 2016 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 "ash/shared/immersive_context.h"
+
+#include "base/logging.h"
+
+namespace ash {
+
+// static
+ImmersiveContext* ImmersiveContext::instance_ = nullptr;
+
+ImmersiveContext::ImmersiveContext() {
+  DCHECK(!instance_);
+  instance_ = this;
+}
+
+ImmersiveContext::~ImmersiveContext() {
+  DCHECK_EQ(instance_, this);
+  instance_ = nullptr;
+}
+
+}  // namespace ash