GitLab

Move PepperPDFHost out of //chrome into the pdf component at //components/pdf.
With this change, the IPC messages in the component is used only by the
component itself, and nothing outside of the component uses these IPC messages
anymore.

BUG=401242
R=raymes@chromium.org, senorblanco@chromium.org, sky@chromium.org, thestig@chromium.org

Review URL: https://codereview.chromium.org/505243003

Cr-Commit-Position: refs/heads/master@{#292416}