Sadly, box.dart has grown much longer than 1000 lines. This patch splits it up
into several files based on the class hierarchy. Fortunately, many of these
classes are loosely coupled to each other.
We had a remarkable number of analyzer failures.
I'll fix the bots to analyze across the whole project
in a follow-up patch, that should prevent this
in the future.
@abarth
This also fixes the C++ side to give the right baseline information.
Previously it was giving the baseline distance for the font, but not
for the actual laid-out text.
I considered also providing a "defaultBaseline" accessor that returns
the distance for the actual dominant baseline, but it turns out right
now we never decide the baseline is ideographic. We always use the
alphabetic baseline. We should probably fix that...
R=eseidel@chromium.org
Review URL: https://codereview.chromium.org/1200233002.
