Remove FetchMainResource and SubstituteData

We are not using loader for main resources anymore.

Bug: 855189
Change-Id: I56c5d04e0088f1ae2c1ce6fe2cee9cbfe3ac90d2
Reviewed-on: https://chromium-review.googlesource.com/c/1424166
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626439}
8 files changed