[Fetch] Use wrapper tracing to express references between wrappers

This is a reland of
https://crrev.com/8057f58cb22579bc685efa50c579325ed047d51a which has
been reverted due to a crash issue. The crash was caused by a missing
TraceWrapperMember in blink::Response. This CL fixes that, and adds
a layout test to verify that.

Original CL: https://chromium-review.googlesource.com/c/1124270

Bug: 862440
Change-Id: I2842b957f223cfb32fee2aa9048b550010cb2e45
Reviewed-on: https://chromium-review.googlesource.com/1134642
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574527}
14 files changed