Add BlimpContents[,Observer] and BlimpNavigationController

blimp/client/core/public/blimp_navigation_controller.h

Index: blimp/client/core/public/blimp_navigation_controller.h
diff --git a/blimp/client/core/public/blimp_navigation_controller.h b/blimp/client/core/public/blimp_navigation_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..fc79b068f21269eac92283111750522dcb009f72
--- /dev/null
+++ b/blimp/client/core/public/blimp_navigation_controller.h
@@ -0,0 +1,42 @@
+// 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.
+
+#ifndef BLIMP_CLIENT_CORE_PUBLIC_BLIMP_NAVIGATION_CONTROLLER_H_
+#define BLIMP_CLIENT_CORE_PUBLIC_BLIMP_NAVIGATION_CONTROLLER_H_
+
+#include "base/macros.h"
+#include "url/gurl.h"
+
+namespace blimp {
+namespace client {
+
+class BlimpContentsObserver;
+
+// The BlimpNavigationController maintains the back-forward list for a
+// BlimpContents and manages all navigation within that list.
+//
+// Each BlimpNavigationController belongs to one BlimpContents, and each
+// BlimpContents has exactly one BlimpNavigationController.
+class BlimpNavigationController {
+ public:
+  virtual ~BlimpNavigationController() = default;
+
+  // Calls to LoadURL informs the engine that it should start navigating to the
+  // provided |url|.
+  virtual void LoadURL(const GURL& url) = 0;
+
+  // Retrieves the URL of the currently selected item in the navigation list.
+  virtual const GURL& GetURL() = 0;
+
+ protected:
+  BlimpNavigationController() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BlimpNavigationController);
+};
+
+}  // namespace client
+}  // namespace blimp
+
+#endif  // BLIMP_CLIENT_CORE_PUBLIC_BLIMP_NAVIGATION_CONTROLLER_H_