Use PredefinedHandle in pup.mojom instead of the full WindowsHandle

RegKeyPath in pup.mojom has the only registry handle passed from the
chrome_cleaner target process to the broker process. This handle is always a
root key (eg. HKCU or HKLM) so it can be represented directly using the
PredefinedHandle enum. This simplifies the serialization slightly and is a
first step to switching to a move-only interface for registry handles.

Also update copyright headers and an obsolete comment on the EngineCommands
interface.

R=wfh

Bug: 830892
Change-Id: I687773b545d199b765345b2a7dd8e310b7609265
Reviewed-on: https://chromium-review.googlesource.com/1197223
Reviewed-by: Will Harris <wfh@chromium.org>
Commit-Queue: Joe Mason <joenotcharles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588869}
9 files changed