[Nearby] Update FakeReceiveManager to match mojo definition.

This just updates the return value of registerForegroundReceiveSurface()
to return an enum. The result is not currently used in any tests, but
this change brings FakeReceiveManager inline with the mojo definition.

Fixed: 1159672
Change-Id: I3e9e8925f7dd497e5590b75e4cdf308c4fb88838
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2601645Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Michael Hansen <hansenmichael@google.com>
Cr-Commit-Position: refs/heads/master@{#839044}

chrome/test/data/webui/settings/chromeos/fake_receive_manager.js

@@ -78,7 +78,8 @@ cr.define('nearby_share', function() {
     }
 
     /**
-     * @return {!Promise<{success: !boolean}>}
+     * @return {!Promise<{result:
+     *     !nearbyShare.mojom.RegisterReceiveSurfaceResult}>}
      */
     async registerForegroundReceiveSurface() {
       this.inHighVisibility_ = true;
@@ -86,7 +87,10 @@ cr.define('nearby_share', function() {
         this.observer_.onHighVisibilityChanged(this.inHighVisibility_);
       }
       this.methodCalled('registerForegroundReceiveSurface');
-      return {success: this.nextResult_};
+      const result = this.nextResult_ ?
+          nearbyShare.mojom.RegisterReceiveSurfaceResult.kSuccess :
+          nearbyShare.mojom.RegisterReceiveSurfaceResult.kFailure;
+      return {result: result};
     }
 
     /**