Apply optical sizing independent of zoom level or device-pixel ratio

Applying optical sizing needs to be done based on specified CSS font
size (taking size-adjust into account), without independent of the page
zoom factor. If the latter is factored in, with zoom-for-dsf, the device
pixel ratio of the screen contributes to what optical size is applied,
leading to wrong results. Example: With a device-pixel-ratio of two, at
font-size 12px an opsz of 24px would be applied, instead of 12px -
leading to unexpected results.

Introduce a new getter on FontDescription which can return the unzoomed
specified font size, including adjustments through size-adjust. Use that
in BinaryFontFaceSource and RemoteFontFaceSource to pass it to the font
instantiation and application of opsz in FontCustomPlatformData.

Add internal WPT tests as clones of the existing opsz tests +
zoom. These can't be external WPT tests as zoom cannot be tested there,
see issue https://github.com/web-platform-tests/wpt/issues/12725.

Fixed: 1305237
Change-Id: I92f2b7d8dc0ea970c28ad84db067b17845e5d961
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3827422
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1034152}