Use single size to request from favicon server in LargeIconService

Currently LargeIconService allows callers to decide the size of the
favicon they wish to download from the favicon server. Depending on
which UI surface the user opens first, a different size is downloaded,
which can cause displaying upscaled icons and decrease in quality. We
solve this by downloading a single sufficiently big size (chosen based
on existing values used by callers), aiming to only have downscaling.

Bug: 982810
Change-Id: Ibad636d4c4d63791e9eb62d99221d9f35c9cb375
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1695268
Commit-Queue: Victor Vianna <victorvianna@google.com>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Kristi Park <kristipark@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Nicolas Zea <zea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681751}