Fix size calculations in ExpandableTextPropertyValue
Fix size calculations in ExpandableTextPropertyValue

Previously, the code calculated the size of the string when using UTF-16
as the encoding. However, UTF-8 is much more common on the web and for
web development, so it makes more sense to use that. This CL changes
the size calculations to use UTF-8 instead.

Bug: 1024721
Change-Id: Iddc5950ffeccb2b561cd5301fb0aba3ec66a873f
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2134287
Reviewed-by: Paul Lewis <8915f5d5c39a08c5a3e8a8d7314756e4580816f9@chromium.org>
Commit-Queue: Surma <e8cf64d4ed46012faceace8e5a40ee721bb47545@chromium.org>

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