Add options to write version number to registry.

Add options to write version number to registry.

The MSI installer creates a DisplayVersion registry entry
with an encoded version of Chrome's actual version.  Since
this is done _after_ the setup call completes, we can't
simply set the value in the normal setup process.  Instead,
we launch a background process that waits a while (for
msiexec to complete) and then writes the updated version.

This is accomplished by having setup, upon successful completion,
run itself in the background and then exit normally.

--set-display-version-path="SOFTWARE\...\InstallProperties"
--set-display-version-value="A.B.C.D"
--delay=30

BUG=67348

Review URL: https://codereview.chromium.org/1271893003

Cr-Commit-Position: refs/heads/master@{#348556}