window interface: add close method

Add a close method, that when called does whatever is appropriate for
the given implementation.

Note: There are a few methods that don't map nicely, and therefore it
makes sense to add a close() to this interface.

Change-Id: If001446b2248715ea76147ea35a99a729ba5a404
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/lpc_handler.cpp b/lpc_handler.cpp
index e5b49a2..32acf1d 100644
--- a/lpc_handler.cpp
+++ b/lpc_handler.cpp
@@ -33,7 +33,7 @@
 
 bool LpcDataHandler::close()
 {
-    /* TODO: implement ioctl call to close window. */
+    mapper->close();
 
     return setInitializedAndReturn(false);
 }