Set keys for SwitchAccessEventHandler to capture using accessibiltyPrivate API

chrome/browser/chromeos/accessibility/switch_access_event_handler.h

Index: chrome/browser/chromeos/accessibility/switch_access_event_handler.h
diff --git a/chrome/browser/chromeos/accessibility/switch_access_event_handler.h b/chrome/browser/chromeos/accessibility/switch_access_event_handler.h
index 331f8363bbe4ae99c1e9284979c711a4db0cae68..4a45cf273d8e816c6a420b527bb786ca9d3d6591 100644
--- a/chrome/browser/chromeos/accessibility/switch_access_event_handler.h
+++ b/chrome/browser/chromeos/accessibility/switch_access_event_handler.h
@@ -5,6 +5,9 @@
 #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"
 
@@ -22,6 +25,8 @@ class SwitchAccessEventHandler : public ui::EventHandler {
   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;
@@ -29,6 +34,8 @@ class SwitchAccessEventHandler : public ui::EventHandler {
   void CancelEvent(ui::Event* event);
   void DispatchKeyEventToSwitchAccess(const ui::KeyEvent& event);
 
+  std::unordered_set<int> captured_keys_;
+
   DISALLOW_COPY_AND_ASSIGN(SwitchAccessEventHandler);
 };