Add regression tests for `underline`.

We're within 4px in every case.

core/tests/regression_tests.rs

@@ -216,6 +216,7 @@ swf_tests_approx! {
     (edittext_margins, "avm1/edittext_margins", 1, 3.0),
     (edittext_tab_stops, "avm1/edittext_tab_stops", 1, 5.0),
     (edittext_bullet, "avm1/edittext_bullet", 1, 3.0),
+    (edittext_underline, "avm1/edittext_underline", 1, 4.0),
 }
 
 /// Wrapper around string slice that makes debug output `{:?}` to print string same way as `{}`.

core/tests/swfs/avm1/edittext_underline/output.txt

@@ -0,0 +1,40 @@
+//Creating left aligned text w/ wordwrap, multiline
+//field.textWidth
+241
+//field.textHeight
+52
+//Creating center aligned text w/ wordwrap, multiline
+//field.textWidth
+237
+//field.textHeight
+52
+//Creating right aligned text w/ wordwrap, multiline
+//field.textWidth
+237
+//field.textHeight
+52
+//Creating justified text w/ wordwrap, multiline
+//field.textWidth
+237
+//field.textHeight
+52
+//Creating left aligned text w/ wordwrap, multiline & long text
+//field.textWidth
+245
+//field.textHeight
+144
+//Creating center aligned text w/ wordwrap, multiline & long text
+//field.textWidth
+241
+//field.textHeight
+144
+//Creating right aligned text w/ wordwrap, multiline & long text
+//field.textWidth
+241
+//field.textHeight
+144
+//Creating justified text w/ wordwrap, multiline & long text
+//field.textWidth
+241
+//field.textHeight
+144