[webauthn] Add WebAuthn DevTools Domain.

Add a DevTools Domain that allows enabling and disabling the WebAuthn Virtual
Authenticator Environment. Eventually the domain will have a set of methods to
add and interact with authenticators.

This patch also removes a race condition from the
devtools/agents-enable-disable.js web test that was made apparent by adding this
domain. Domains' `.disable` methods are no longer assumed to be finish in the
same order as their `.enable` methods.

For an overview of the overall design, please see
https://docs.google.com/document/d/1bp2cMgjm2HSpvL9-WsJoIQMsBi1oKGQY6CvWD-9WmIQ/edit?usp=sharing

Bug: 922572
Change-Id: Id43c184e5830de72736410049fdacba9a965a6d3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617550
Commit-Queue: Nina Satragno <[email protected]>
Reviewed-by: Andrey Kosyakov <[email protected]>
Reviewed-by: Kim Paulhamus <[email protected]>
Reviewed-by: Alexei Filippov <[email protected]>
Cr-Commit-Position: refs/heads/master@{#664392}
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 96a0295a..ae67cb6 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -2496,9 +2496,15 @@
   } else {
     # Not Android.
     sources += [
+      # The WebAuthn devtools protocol API is not supported in Android yet.
+      "$target_gen_dir/devtools/protocol/web_authn.cc",
+      "$target_gen_dir/devtools/protocol/web_authn.h",
+
       # Devtools frontend not included in Android
       "devtools/devtools_frontend_host_impl.cc",
       "devtools/devtools_frontend_host_impl.h",
+      "devtools/protocol/webauthn_handler.cc",
+      "devtools/protocol/webauthn_handler.h",
       "host_zoom_level_context.cc",
       "host_zoom_level_context.h",
       "host_zoom_map_impl.cc",