Set keys for SwitchAccessEventHandler to capture using accessibiltyPrivate API

chrome/browser/chromeos/accessibility/switch_access_event_handler.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 CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_SWITCH_ACCESS_EVENT_HANDLER_H_
 #define CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_SWITCH_ACCESS_EVENT_HANDLER_H_
 
+#include <string>

[Devlin, 2017/05/30 19:22:03]

not needed

[elichtenberg, 2017/05/31 00:58:43]

Done.

+#include <unordered_set>
+
 #include "base/macros.h"
 #include "ui/events/event_handler.h"
 
 namespace chromeos {
 
 // When Switch Access is enabled, intercepts a few keys before the rest of the
 // OS has a chance to handle them, as a method for controlling the entire OS
 // with a small number of switches. The key events do not propagate to the rest
 // of the system.
 //
 // This class just intercepts the keys and forwards them to the component
 // extension.
 class SwitchAccessEventHandler : public ui::EventHandler {
  public:
   SwitchAccessEventHandler();
   ~SwitchAccessEventHandler() override;
 
+  void SetKeysToCapture(const std::unordered_set<int>& key_codes);

[Devlin, 2017/05/30 19:22:03]

Any reason to use std::unordered_set over std::set?

[elichtenberg, 2017/05/31 00:58:43]

I believe unordered_sets are faster than sets. I think unordered_sets are
hashsets, and sets are binary search trees.

[Devlin, 2017/05/31 01:33:32]

"faster" depends entirely on data set size.  The algorithmic lookup complexity
is faster, but for small data sets (like this), a regular std::set is likely
faster, and certainly less memory (a vector would be better yet, but doesn't
have the de-duping/counting niceties of a set).  Unless there's a very concrete
reason to use the unordered counterparts (i.e., known to be large data sets and
performance-sensitive code), prefer using the vanilla std::set.  (The same goes
for std::map vs std::unordered_map.)

I think brettw@ wrote up a nice post in chromium-dev that highlights this, along
with some more scientific measurements, awhile back.

[elichtenberg, 2017/06/01 19:55:26]

Fair point. Changed it to std::set.

+
  private:
   // EventHandler:
   void OnKeyEvent(ui::KeyEvent* event) override;
 
   void CancelEvent(ui::Event* event);
   void DispatchKeyEventToSwitchAccess(const ui::KeyEvent& event);
 
+  std::unordered_set<int> captured_keys_;
+
   DISALLOW_COPY_AND_ASSIGN(SwitchAccessEventHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_SWITCH_ACCESS_EVENT_HANDLER_H_