perfetto-ui: Prefetch resources required resources
perfetto-ui: Prefetch resources required resources

We know we're going to need controller_bundle.js, engine_bundle.js, and
trace_processor.wasm but the browser can't tell this until we request
them via Javascript. Preloading them allows for the downloading to
happen in parallel. Devtools complains that the resources are unused but
I'm pretty sure it's wrong - looking at the network tab shows it helps.

Change-Id: Iab0813a2f9359d2c88bacd7853f9dda89f49f114
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto