Prefer std::string over String8

String8 is obsolete, only use std::string in the
input libraries now.

Bug: 64258224
Test: make
Change-Id: I958b6b281d969138f39cc26825c877a24bc4a853
diff --git a/services/inputflinger/Android.bp b/services/inputflinger/Android.bp
index 238cba3..a9e5a43 100644
--- a/services/inputflinger/Android.bp
+++ b/services/inputflinger/Android.bp
@@ -26,6 +26,7 @@
     ],
 
     shared_libs: [
+        "libbase",
         "libbinder",
         "libcrypto",
         "libcutils",