Add touch events to the protocol, the stub layer, and to the client plugin.

remoting/host/fake_desktop_environment.cc

Index: remoting/host/fake_desktop_environment.cc
diff --git a/remoting/host/fake_desktop_environment.cc b/remoting/host/fake_desktop_environment.cc
index 7f84b6e15f551d5d32437750e323d0f9166a0b4b..bff63233c46bd7666e746c85a12787121ad042b9 100644
--- a/remoting/host/fake_desktop_environment.cc
+++ b/remoting/host/fake_desktop_environment.cc
@@ -27,6 +27,9 @@ void FakeInputInjector::InjectTextEvent(const protocol::TextEvent& event) {
 void FakeInputInjector::InjectMouseEvent(const protocol::MouseEvent& event) {
 }
 
+void FakeInputInjector::InjectTouchEvent(const protocol::TouchEvent& event) {
+}
+
 void FakeInputInjector::InjectClipboardEvent(
     const protocol::ClipboardEvent& event) {
 }