commit 9bde1c28917f5efc4e553720d09a1c194540de97
author Tibor Goldschwendt <tiborg@chromium.org> Sat May 09 00:06:13 2020
committer Commit Bot <commit-bot@chromium.org> Sat May 09 00:06:13 2020
tree 63fa9f3bb0c48524e3d7d69aba933f59aaf67414
parent 19f6987d0720ab34667ed531f50a9ec11b223732

[webui][ntp] Load background image earlier during startup

Reduces the duration until the background image is loaded
(background-image-loaded metric) from ~312ms to ~112ms (~2.8x
improvement) upon opening a new tab.

This is accomplished by two optimizations:
1. Baking the initial background image URL into the NTP via load time
   data. Thus, no JS has to run to set the URL.
2. Moving the background image iframe out of <ntp-app> into the NTP main
   HTML. Thus, we don't have to wait for Polymer to create the DOM
   before the image load is triggered.

<ntp-app> still owns the business logic controlling the image's
visibility and URL update. <ntp-app> will now communicate those changes
to the BackgroundManager, which in turn manifests those changes into the
DOM, hence abstracting away the ownership of the background image
iframe. The same applies to the background color, which is set on the
body now to keep being behind the background image.

Bug: 1061078
Change-Id: I0151cc52f3bc049238ae321d90106a3c416cc970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2183482
Commit-Queue: Tibor Goldschwendt <tiborg@chromium.org>
Reviewed-by: dpapad <dpapad@chromium.org>
Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#767060}