Provide a library interface to the virtual touchpad service.

And make VrWindowManager pay for^H^H^H^H^H^H^H^H use it. The library
interface is a step toward moving 2D embedding into VrCore because it
hides the binder connection that isn't directly accessible to VrCore.

As a matter of implementation, the touchpad-service client library
and the low-level evdev touchpad are derived from the same interface.

Bug: b/35990873
Test: VirtualTouchpad_test; integration TBD.
Change-Id: Ic922ff223ddd5a44f6fb4433a271f8341e93a0e7
diff --git a/services/vr/virtual_touchpad/VirtualTouchpadService.cpp b/services/vr/virtual_touchpad/VirtualTouchpadService.cpp
index 25c1a4f..3fcb8fc 100644
--- a/services/vr/virtual_touchpad/VirtualTouchpadService.cpp
+++ b/services/vr/virtual_touchpad/VirtualTouchpadService.cpp
@@ -8,19 +8,15 @@
 namespace android {
 namespace dvr {
 
-int VirtualTouchpadService::Initialize() {
-  return touchpad_.Initialize();
-}
-
 binder::Status VirtualTouchpadService::touch(float x, float y, float pressure) {
-  const int error = touchpad_.Touch(x, y, pressure);
-  return error ? binder::Status::fromServiceSpecificError(error)
+  const status_t error = touchpad_->Touch(x, y, pressure);
+  return error ? binder::Status::fromStatusT(error)
                : binder::Status::ok();
 }
 
 binder::Status VirtualTouchpadService::buttonState(int buttons) {
-  const int error = touchpad_.ButtonState(buttons);
-  return error ? binder::Status::fromServiceSpecificError(error)
+  const status_t error = touchpad_->ButtonState(buttons);
+  return error ? binder::Status::fromStatusT(error)
                : binder::Status::ok();
 }