Save navigation gesture directly in the document loader

Instead of getting it in DidStartProvisionalLoad and then
using in DidCommitProvisionalLoad, we can just ask
DocumentLoader whether it had a user gesture.

This is a step towards removing DidStartProvisionalLoad.

Bug: 855189
Change-Id: I9e1f47f532e7d2b0e0def7f988dff51569fd0f4b
Reviewed-on: https://chromium-review.googlesource.com/1220671
Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591155}
9 files changed