Add hashCode to InputMethodInfo

The uniqueness of InputMethodInfo was guaranteed by mId (like InputMethodInfo#equals), but the hashCode was not implemented in the same way.
This change fixes a problem happening when the user gets the hashCode of InputMethodInfo obtained through IPC.

Change-Id: Ib876c5cb0d778481100597ec31202f94fb7b8f37

api/current.xml

@@ -267763,7 +267763,7 @@
  deprecated="not deprecated"
  visibility="public"
 >
-<parameter name="arg0" type="T">
+<parameter name="t" type="T">
 </parameter>
 </method>
 </interface>

core/java/android/view/inputmethod/InputMethodInfo.java

@@ -322,7 +322,12 @@ public final class InputMethodInfo implements Parcelable {
         InputMethodInfo obj = (InputMethodInfo) o;
         return mId.equals(obj.mId);
     }
-    
+
+    @Override
+    public int hashCode() {
+        return mId.hashCode();
+    }
+
     /**
      * Used to package this object into a {@link Parcel}.
      *