ui: small fixes to service worker / offline support
ui: small fixes to service worker / offline support

This CL does three things:
1. Fix cache misses on /
   The GCS detection logic was wrong and was kicking in also for
   the production URL. Making it more explicit.
2. Speculatively fix b/148070765. Seems originating from a
   chromium bug. An internal search suggests that checking for
   'only-if-cached' && !'same-origin' is the right thing to do.
3. Rework the network bypass logic. Instead of handling the fetch
   and re-fetching in the service worker, just don't call
   .respondWith() for cases that shouldn't be handled. This has
   also the nice side-effect that reduces the spam in case of
   expected fetch errors (e.g. the 127.0.0.1 for the RPC).

Bug: 147015767
Bug: 148070765
Change-Id: I07d25aabfc5eba512fddfb59a19351ae3b01fd6a

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto