Print Preview: Remove use-cloud-print event

This event can cause a race condition in release build tests, since the
real event can fire after the original instance of print-preview-app is
removed from the DOM and the new one has been attached. This can result
in multiple use-cloud-print events (one real, one test) in tests of
cloud print behavior. This race condition appears to be exposed by
waiting for the HTML Imports polyfill and element definition, which are
necessary changes for migrating Print Preview to use the polyfill.

There is also no need for a separate event now that Print Preview is
using cr.sendWithPromise to handle initial settings instead of relying
on chrome.send and multiple calls to CallJavascriptFunctionUnsafe, which
needed to be ordered on the C++ side. Instead, we can send the cloud
print URL in the initial settings if cloud print is enabled, and always
set the cloud print interface before initializing the DestinationStore
in JS to guarantee that autoselection of cloud printers works.

Bug: 925517
Change-Id: Ifa84ef832ee8d129ab25ab5bfdb0f33882d1b48a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1576120
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652743}
7 files changed