Add type alias for DeviceId

To facilitate the future transition to a strong type, add a "weak" type
for DeviceId in this CL.

This will allow us to fix some of the existing code before having to
refactor all of it in a single topic.

Also, in this CL, simplify the names of some variables in TouchState
because we no longer have a conflict with the 'deviceId' member.

Bug: 211379801
Test: none
Change-Id: I1f287ad62fa26ba4bbbbbf353bebfbf8ad38ff67
diff --git a/services/inputflinger/dispatcher/InputState.h b/services/inputflinger/dispatcher/InputState.h
index af2a3cb..e741137 100644
--- a/services/inputflinger/dispatcher/InputState.h
+++ b/services/inputflinger/dispatcher/InputState.h
@@ -36,7 +36,7 @@
 
     // Returns true if the specified source is known to have received a hover enter
     // motion event.
-    bool isHovering(int32_t deviceId, uint32_t source, int32_t displayId) const;
+    bool isHovering(DeviceId deviceId, uint32_t source, int32_t displayId) const;
 
     // Records tracking information for a key event that has just been published.
     // Returns true if the event should be delivered, false if it is inconsistent
@@ -76,7 +76,7 @@
 
 private:
     struct KeyMemento {
-        int32_t deviceId;
+        DeviceId deviceId;
         uint32_t source;
         int32_t displayId;
         int32_t keyCode;
@@ -88,7 +88,7 @@
     };
 
     struct MotionMemento {
-        int32_t deviceId;
+        DeviceId deviceId;
         uint32_t source;
         int32_t displayId;
         int32_t flags;