Enable keyboard filters in PNaCl client

remoting/client/plugin/normalizing_input_filter_mac.h

Index: remoting/client/plugin/normalizing_input_filter_mac.h
diff --git a/remoting/client/plugin/normalizing_input_filter_mac.h b/remoting/client/plugin/normalizing_input_filter_mac.h
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+// Copyright 2014 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 <map>
+
+#include "remoting/protocol/input_filter.h"
+
+namespace remoting {
+
+// NormalizingInputFilterMac is designed to solve the problem of missing keyup
+// events on Mac.
+//
+// PROBLEM
+//
+// On Mac if user presses CMD and then C key there is no keyup event generated
+// for C when user releases the C key before the CMD key.
+// The cause is that CMD + C triggers a system action and Chrome injects only a
+// keydown event for the C key. Safari shares the same behavior.
+//
+// SOLUTION
+//
+// When a keyup event for CMD key happens we will check all prior keydown
+// events received and inject corresponding keyup events artificially, with
+// the exception of:
+//
+// SHIFT, CONTROL, OPTION, LEFT CMD, RIGHT CMD and CAPS LOCK
+//
+// because they are reported by Chrome correctly.
+//
+// There are a couple cases that this solution doesn't work perfectly, one
+// of them leads to duplicated keyup events.
+//
+// User performs this sequence of actions:
+//
+// CMD DOWN, C DOWN, CMD UP, C UP
+//
+// In this case the algorithm will generate:
+//
+// CMD DOWN, C DOWN, C UP, CMD UP, C UP
+//
+// Because we artificially generate keyup events the C UP event is duplicated
+// as user releases the key after CMD key. This would not be a problem as the
+// receiver end will drop this duplicated keyup event.
+class NormalizingInputFilterMac : public protocol::InputFilter {
+ public:
+  explicit NormalizingInputFilterMac(protocol::InputStub* input_stub);
+  virtual ~NormalizingInputFilterMac();
+
+  // InputFilter overrides.
+  virtual void InjectKeyEvent(const protocol::KeyEvent& event) OVERRIDE;
+
+ private:
+  typedef std::map<int, protocol::KeyEvent> KeyPressedMap;
+
+  // Generate keyup events for any keys pressed with CMD.
+  void GenerateKeyupEvents();
+
+  // A map that stores pressed keycodes and the corresponding key event.
+  KeyPressedMap key_pressed_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(NormalizingInputFilterMac);
+};
+
+}  // namespace remoting