webauthn: put credProps behind WebAuthenticationResidentKeyRequirement flag

CL:2410419 added support for the WebAuthn credProps extension. I meant
to guard it with the WebAuthenticationResidentKeyRequirement, but
accidentally commented out the relevant line.

Thanks to Shane Weeden for spotting this issue.

Bug: 1117630
Change-Id: I96f6bac63cd3093f333891ba7a54c0c471d304ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2500956
Auto-Submit: Martin Kreichgauer <martinkr@google.com>
Commit-Queue: Nina Satragno <nsatragno@chromium.org>
Reviewed-by: Nina Satragno <nsatragno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821262}

third_party/blink/renderer/modules/credentialmanager/authentication_extensions_client_inputs.idl

@@ -24,8 +24,7 @@ dictionary AuthenticationExtensionsClientInputs {
   boolean enforceCredentialProtectionPolicy = false;
 
   // https://w3c.github.io/webauthn/#sctn-authenticator-credential-properties-extension
-  // [RuntimeEnabled=WebAuthenticationResidentKeyRequirement]
-  boolean credProps = false;
+  [RuntimeEnabled=WebAuthenticationResidentKeyRequirement] boolean credProps = false;
 
   // https://w3c.github.io/webauthn/#sctn-large-blob-extension
   [RuntimeEnabled=WebAuthenticationLargeBlobExtension] AuthenticationExtensionsLargeBlobInputs largeBlob;