Switch the default U2F attestation behaviour to "none".

Bug: 793985
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I19f4c1e2cff81b41a919449b926616d5e0f9d813
Reviewed-on: https://chromium-review.googlesource.com/899674Reviewed-by: David Benjamin <davidben@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534135}

chrome/browser/resources/cryptotoken/enroller.js

@@ -338,10 +338,11 @@ var ConveyancePreference = {
  */
 function conveyancePreference(enrollChallenge) {
   if (enrollChallenge.hasOwnProperty('attestation') &&
-      enrollChallenge['attestation'] == 'none') {
-    return ConveyancePreference.NONE;
+      (enrollChallenge['attestation'] == 'direct' ||
+       enrollChallenge['attestation'] == 'indirect')) {
+    return ConveyancePreference.DIRECT;
   }
-  return ConveyancePreference.DIRECT;
+  return ConveyancePreference.NONE;
 }
 
 /**