Add APIs to the client plugin to re-map and trap key events.

remoting/protocol/input_filter.cc

 // Copyright (c) 2012 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 "remoting/protocol/input_filter.h"
 
 namespace remoting {
 namespace protocol {
 
 InputFilter::InputFilter() : input_stub_(NULL) {
 }
 
+InputFilter::InputFilter(InputStub* input_stub) : input_stub_(input_stub) {
+}
+
 InputFilter::~InputFilter() {
 }
 
 void InputFilter::InjectKeyEvent(const KeyEvent& event) {
   if (input_stub_ != NULL)
     input_stub_->InjectKeyEvent(event);
 }
 
 void InputFilter::InjectMouseEvent(const MouseEvent& event) {
   if (input_stub_ != NULL)
     input_stub_->InjectMouseEvent(event);
 }
 
 }  // namespace protocol
 }  // namespace remoting