Remove substitute data from WebNavigationParams

We can fill response and body_loader instead, and have (almost) a single
code path when loading.

Bug: 855189
Change-Id: Ifc092211e2820ec8ef24cf77319e52cd2fa2907d
Reviewed-on: https://chromium-review.googlesource.com/c/1423461
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627056}
6 files changed