Reland "Add touch selection for PDF files.""

This reverts commit 0d7094b3c580b9da58028691e5936026a2b3ed91.

> Add touch selection for PDF files.
>
> This CL plumbs through the need methods to allow touch selection with
> the Copy action in PDF files.
>
> Bug: chromium:490184, chromium:737585
> Change-Id: I4dab62833dac94b6c8ed59cbcc7db8e9387a7fde
> Reviewed-on: https://chromium-review.googlesource.com/565899
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Reviewed-by: Tom Sepez <tsepez@chromium.org>
> Reviewed-by: John Abd-El-Malek <jam@chromium.org>
> Reviewed-by: Raymes Khoury <raymes@chromium.org>
> Reviewed-by: James MacLean <wjmaclean@chromium.org>
> Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#489071}

TBR=jam@chromium.org,tsepez@chromium.org,raymes@chromium.org

Bug: chromium:490184, chromium:737585, chromium:748390
Change-Id: Ief608baf13b1a5c04e19c9d7c2e7398e8d1c8cb5
Reviewed-on: https://chromium-review.googlesource.com/585107
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#489429}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f50e9f3557742f92ff33521a24988578ba8fa88f
12 files changed