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

remoting/protocol/input_filter.cc

Index: remoting/protocol/input_filter.cc
diff --git a/remoting/protocol/input_filter.cc b/remoting/protocol/input_filter.cc
index 44bc24726165582a51e7952c6c00d5e3b4a87e71..83e9122d7b414c7eb1807a8b7ce14fa5363b22e0 100644
--- a/remoting/protocol/input_filter.cc
+++ b/remoting/protocol/input_filter.cc
@@ -32,5 +32,10 @@ void InputFilter::InjectMouseEvent(const MouseEvent& event) {
     input_stub_->InjectMouseEvent(event);
 }
 
+void InputFilter::InjectTouchEvent(const TouchEvent& event) {
+  if (enabled_ && input_stub_ != nullptr)
+    input_stub_->InjectTouchEvent(event);
+}
+
 }  // namespace protocol
 }  // namespace remoting