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This is a refactor CL and it should not change any existing UI.

The affected pages are as follows:
- On startup site entry in chrome://settings
- chrome://settings/siteData
- chrome://settings/searchEngines
- chrome://settings/content/zoomLevels
- chrome://settings/handlers
- chrome://settings/content/usbDevices
- chrome://settings/content/all
- All the pages in "Content settings" that use site-list-entry, such as
  chrome://settings/content/paymentHandler

Bug: 890118
Change-Id: I35e00406999cf30012db557b10dd418cef67a69d
Reviewed-on: https://chromium-review.googlesource.com/c/1277995
Commit-Queue: Yue Cen <rsgingerrs@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602099}