Do not handle data urls in DocumentLoader

This functionality is only used in tests and interstitial pages.
We can instead parse data urls on the call sites and require body
loader to always be present.

Ideally, we should get rid of the special case in RenderFrameImpl,
but current implementation of interstitial pages prevents that.

Bug: 855189
Change-Id: Ic09b2ac641f2a3742d5f38b2f5f8cea2283b43f5
Reviewed-on: https://chromium-review.googlesource.com/c/1436138
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629343}
7 files changed