This patch finally adds the actual calculation that goes into calc()
expressions. When the resolution of a Length that is a calculated value
the parsed CalculatedStyleValue gets traversed and appropriate values
get calculated.
This is a bit hackish, but this way the existance of the calc()
becomes transparent to the user who just wants a Length and doesn't
care where it came from.
Our "frame" concept very closely matches what the web specs call a
"browsing context", so let's rename it to that. :^)
The "main frame" becomes the "top-level browsing context",
and "sub-frames" are now "nested browsing contexts".
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
