poll: Enlarge and vetically center vote count box

Previously, there were only bottom and end paddings; we redistribute
the vertical paddings so the vote count box is padded on both sides.

The end padding remains 5px because we want to keep the options aligned
to the start with the surrounding messages.

The inner padding defined on the Container is affected by
the size of the text.  Document that fact as we make the green box
and the text in it larger.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/widgets/poll.dart

@@ -60,6 +60,7 @@ class _PollWidgetState extends State<PollWidget> {
           style: textStyleBold.copyWith(fontSize: 18, fontStyle: FontStyle.italic));
 
     Widget buildOptionItem(PollOption option) {
+      const verticalPadding = 2.5;
       // TODO(i18n): List formatting, like you can do in JavaScript:
       //   new Intl.ListFormat('ja').format(['Chris', 'Greg', 'Alya', 'Zixuan'])
       //   // 'Chris、Greg、Alya、Zixuan'
@@ -73,10 +74,15 @@ class _PollWidgetState extends State<PollWidget> {
         textBaseline: localizedTextBaseline(context),
         children: [
           ConstrainedBox(
-            constraints: const BoxConstraints(minWidth: 25 + 5).tighten(height: 25 + 5),
+            constraints: const BoxConstraints(
+              minWidth: 39 + 5).tighten(height: 39 + verticalPadding * 2),
             child: Padding(
-              padding: const EdgeInsetsDirectional.only(bottom: 5, end: 5),
+              padding: const EdgeInsetsDirectional.only(
+                end: 5, top: verticalPadding, bottom: verticalPadding),
               child: Container(
+                // Inner padding preserves whitespace even when the text's
+                // width approaches the button's min-width (e.g. because
+                // there are more than three digits).
                 padding: const EdgeInsets.symmetric(horizontal: 4),
                 decoration: BoxDecoration(
                   color: theme.colorPollVoteCountBackground,
@@ -86,7 +92,7 @@ class _PollWidgetState extends State<PollWidget> {
                   child: Text(option.voters.length.toString(),
                     textAlign: TextAlign.center,
                     style: textStyleBold.copyWith(
-                      color: theme.colorPollVoteCountText, fontSize: 13)))))),
+                      color: theme.colorPollVoteCountText, fontSize: 20)))))),
           Expanded(
             child: Wrap(
               spacing: 5,