Keyboard Lock Host implementation

components/keyboard_lock/key_hook.h

Index: components/keyboard_lock/key_hook.h
diff --git a/components/keyboard_lock/key_hook.h b/components/keyboard_lock/key_hook.h
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+++ b/components/keyboard_lock/key_hook.h
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+// 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 COMPONENTS_KEYBOARD_LOCK_KEY_HOOK_H_
+#define COMPONENTS_KEYBOARD_LOCK_KEY_HOOK_H_
+
+#include <vector>
+
+#include "base/callback.h"
+#include "ui/events/keycodes/keyboard_codes.h"
+
+namespace keyboard_lock {
+
+// An interface to register and unregister key codes from low level callback.
+// The implementation needs to guarantee the thread-safety of RegisterKey() and
+// UnregisterKey() functions, which may be executed in both UI thread and
+// network thread.
+class KeyHook {
+ public:
+  KeyHook() = default;
+  virtual ~KeyHook() = default;
+
+  // The |on_result| callback will be called with the result if it's not null.
+  // Calling |on_result| with |false| indicates the failure of an OK API
+  // invoking. Thus, the required ui::KeyboardCode may not be able to received.
+  virtual void RegisterKey(const std::vector<ui::KeyboardCode>& codes,
+                           base::Callback<void(bool)> on_result) = 0;
+  virtual void UnregisterKey(const std::vector<ui::KeyboardCode>& codes,
+                             base::Callback<void(bool)> on_result) = 0;
+};
+
+}  // namespace keyboard_lock
+
+#endif  // COMPONENTS_KEYBOARD_LOCK_KEY_HOOK_H_