Use an ellipsis to clip wide cards_demo titles (#4604)

examples/flutter_gallery/lib/demo/cards_demo.dart

@@ -74,7 +74,11 @@ class TravelDestinationItem extends StatelessWidget {
                   new Positioned(
                     bottom: 16.0,
                     left: 16.0,
-                    child: new Text(destination.title, style: titleStyle)
+                    child: new Text(destination.title,
+                      style: titleStyle,
+                      softWrap: false,
+                      overflow: TextOverflow.ellipsis
+                    )
                   )
                 ]
               )
@@ -83,16 +87,21 @@ class TravelDestinationItem extends StatelessWidget {
             new Flexible(
               child: new Padding(
                 padding: const EdgeInsets.fromLTRB(16.0, 16.0, 16.0, 0.0),
+                child: new DefaultTextStyle(
+                  softWrap: false,
+                  overflow: TextOverflow.ellipsis,
+                  style: descriptionStyle,
                   child: new Column(
                     crossAxisAlignment: CrossAxisAlignment.start,
                     children: <Widget>[
                       // three line description
-                    new Text(destination.description[0], style: descriptionStyle),
-                    new Text(destination.description[1], style: descriptionStyle),
-                    new Text(destination.description[2], style: descriptionStyle),
+                      new Text(destination.description[0]),
+                      new Text(destination.description[1]),
+                      new Text(destination.description[2]),
                     ]
                   )
                 )
+              )
             ),
             // share, explore buttons
             // TODO(abarth): The theme and the bar should be part of card.