There was a subtle mismatch between the obviously expected behavior
of BumpAllocator::for_each_chunk() and its actual implementation.
You'd think it would invoke the callback with the address of each chunk,
but actually it also took the liberty of adding sizeof(ChunkHeader) to
this address. UniformBumpAllocator::destroy_all() relied on this to
get the right address for objects to delete.
The bug happened in BumpAllocator::deallocate_all(), where we use
for_each_chunk() to walk the list of chunks and munmap() them.
To avoid memory mapping churn, we keep a global cache of 1 chunk around.
Since we were being called with the offset chunk address, it meant that
the cached chunk shifted 16 bytes away from its real address every time
we re-added it to the cache.
Eventually the cached chunk address would leave its memory region
entirely, and at that point, any attempt to allocate from it would yield
an address outside the region, causing memory corruption.
This change makes calculate_static_position to return content box
for both x and y (at least for the case when children are not inline).
It makes it possible to be consistent about x and y when calculating
box offset inside layout_absolutely_positioned_element.
We were mistakenly trying to append UTF-16 code units to a StringBuilder
via the append(char) API. This patch fixes that by accumulating the
result in a Vector<u16> instead.
This'll be a bit worse for performance, since we're now doing additional
UTF-16 string conversions, but we're going for correctness at this stage
and can worry about performance later.
Because of how we output lines in the loop above, if we leave that loop
when the last line was not the same in both files, then either
`file1_line` or `file2_line` has not been output yet.
`process_remaining()` does not print that line either, since it
immediately reads a new line. So, output the previously-missing line
before we call that. :^)
