libui: use unique_fd in Fence

Use unique_fd internally.  Add a constructor to create a Fence from
a unique_fd.

Test: boots
Change-Id: I36e7a337885a6559ed6fe82c56b718f56108aaf8
diff --git a/libs/ui/Android.bp b/libs/ui/Android.bp
index 102964f..abe856e 100644
--- a/libs/ui/Android.bp
+++ b/libs/ui/Android.bp
@@ -95,6 +95,7 @@
     ],
 
     header_libs: [
+        "libbase_headers",
         "libnativebase_headers",
         "libhardware_headers",
     ],
@@ -107,6 +108,7 @@
     ],
 
     export_header_lib_headers: [
+        "libbase_headers",
         "libnativebase_headers",
         "libhardware_headers",
     ],