When running the WebVR layout tests, the following lines are always output:

19:07:59.183 22403   [23842:23881:0308/190758.703989:8285176142:WARNING:url_request_job_manager.cc(90)] Failed to map: layout-test-mojom://content/shell/renderer/layout_test/frame_interface_registry
19:07:59.183 22403   [23842:23881:0308/190758.705782:8285177931:WARNING:url_request_job_manager.cc(90)] Failed to map: layout-test-mojom://content/shell/renderer/layout_test/interface_registry
19:07:59.183 22403   [23842:23881:0308/190758.717483:8285189637:WARNING:url_request_job_manager.cc(90)] Failed to map: layout-test-mojom://Mojo Helpers
19:07:59.183 22403   [1:1:0308/190758.865834:8285338193:ERROR:mojo_context_state.cc(199)] Failed to fetch source for module "content/shell/renderer/layout_test/frame_interface_registry"
19:07:59.183 22403   [1:1:0308/190758.867599:8285339879:ERROR:mojo_context_state.cc(199)] Failed to fetch source for module "content/shell/renderer/layout_test/interface_registry"
19:07:59.183 22403   [1:1:0308/190758.870367:8285342662:ERROR:mojo_context_state.cc(199)] Failed to fetch source for module "Mojo Helpers"

They don't cause any issues with the tests themselves, but they should be fixed anyways to help avoid confusion when looking at logs.