added another sample

ui-samples-plugin/src/main/java/jenkins/plugins/ui_samples/ProgressBar.java

+package jenkins.plugins.ui_samples;
+
+import hudson.Extension;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * @author Kohsuke Kawaguchi
+ */
+@Extension
+public class ProgressBar extends UISample {
+    @Override
+    public String getDescription() {
+        return "Shows you how to use the progress bar widget that's used in the executor view and other places";
+    }
+
+    public List<SourceFile> getSourceFiles() {
+        // TODO: generate this from index
+        return Arrays.asList(
+                // new SourceFile(getClass().getSimpleName() + ".java"),  // nothing interesting in the Java source file
+                new SourceFile("index.groovy"));
+    }
+
+    @Extension
+    public static final class DescriptorImpl extends UISampleDescriptor {
+    }
+}
+

ui-samples-plugin/src/main/resources/jenkins/plugins/ui_samples/ProgressBar/index.groovy

+package jenkins.plugins.ui_samples.ProgressBar;
+
+import lib.JenkinsTagLib
+
+def st=namespace("jelly:stapler")
+
+t=namespace(JenkinsTagLib.class)
+
+namespace("/lib/samples").sample(title:_("Progress Bar")) {
+    // in this sample, we add extra margin around them
+    style(".progress-bar {margin:1em;}")
+    p("This page shows you how to use the progress bar widget")
+
+    p("The 'pos' parameter controls the degree of progress, 0-100")
+    t.progressBar(pos:30)
+    t.progressBar(pos:60)
+    t.progressBar(pos:90)
+    p("-1 will draw the progress bar in the 'indeterminate' state");
+    t.progressBar(pos:-1)
+
+    p("The 'red' parameter turns the progress bar to red. Used to indicate that it's overdue")
+    t.progressBar(pos:99, red:true)
+    t.progressBar(pos:-1, red:true)
+
+    p("Tooltip can be added with the 'tooltip' parameter. It can contain arbitrary HTML. Hover your mouse below to see.")
+    t.progressBar(pos:70, tooltip:"Allows <b>arbitrary</b> html")
+
+    p("Hyperlink can be added with the 'href' pointer. Click the progress bar below")
+    t.progressBar(pos:70, href:"http://jenkins-ci.org/")
+}