Forward declare enum to save a #include.

This #include pulls in quite a lot of headers in render_frame_host.h, a
fairly core header.

Change-Id: I17288f2e166ec15880ebac6a11f07c574b16d94b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2553021
Commit-Queue: Adam Langley <agl@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Auto-Submit: Adam Langley <agl@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833096}

content/public/browser/render_frame_host.h

@@ -34,7 +34,6 @@
 #include "third_party/blink/public/mojom/frame/sudden_termination_disabler_type.mojom.h"
 #include "third_party/blink/public/mojom/frame/user_activation_notification_type.mojom.h"
 #include "third_party/blink/public/mojom/loader/pause_subresource_loading_handle.mojom-forward.h"
-#include "third_party/blink/public/mojom/webauthn/authenticator.mojom.h"
 #include "ui/accessibility/ax_tree_id.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/native_widget_types.h"
@@ -44,6 +43,7 @@
 namespace blink {
 class AssociatedInterfaceProvider;
 namespace mojom {
+enum class AuthenticatorStatus;
 enum class FeaturePolicyFeature;
 }  // namespace mojom
 }  // namespace blink