Move FrameHostMsg_GoToEntryAtOffset to mojo

This CL changes FrameHostMsg_GoToEntryAtOffset so that it is
implemented in the LocalFrameHost interface.

It removes WebLocalFrameClient::NavigateBackForwardSoon() from
web_local_frame_client.h since LocalFrameClientImpl have access to
mojom::blink::LocalFrameHost.

Bug: 1039286
Change-Id: If565c4fffb3f785d3518dc38171cf7092c7ef30d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2000267
Commit-Queue: Julie Kim <jkim@igalia.com>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733150}
15 files changed