Add a UMA for same-originness of classic worker top-level scripts

To investigate when/how often there are "cross-origin" workers,
this CL adds a UMA to record same-originness of worker scripts
and its cross-origin reasons of classic worker top-level scripts.

Bug: 867302
Change-Id: I52c8caab6974d2db0b95e25115faba8045429902
Reviewed-on: https://chromium-review.googlesource.com/c/1149325
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616566}
3 files changed