https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_ubsan_rel_ng/builds/77

Failure message:

../../chrome/browser/ui/webui/media_router/media_router_ui.cc:844:10: runtime error: downcast of address 0x25c46d0af050 which does not point to an object of type 'media_router::MediaRouterMojoImpl'
0x25c46d0af050: note: object is of type 'media_router::MockMediaRouter'