[SPARK-10864][WEB UI] app name is hidden if window is resized

Currently the Web UI navbar has a minimum width of 1200px; so if a window is resized smaller than that the app name goes off screen. The 1200px width seems to have been chosen since it fits the longest example app name without wrapping.

To work with smaller window widths I made the tabs wrap since it looked better than wrapping the app name. This is a distinct change in how the navbar looks and I'm not sure if it's what we actually want to do.

Other notes:
- min-width set to 600px to keep the tabs from wrapping individually (will need to be adjusted if tabs are added)
- app name will also wrap (making three levels) if a really really long app name is used

Author: Alex Bozarth <ajbozart@us.ibm.com>

Closes #9874 from ajbozarth/spark10864.

core/src/main/resources/org/apache/spark/ui/static/webui.css

@@ -16,14 +16,9 @@
  */
 
 .navbar {
-  height: 50px;
   font-size: 15px;
   margin-bottom: 15px;
-  min-width: 1200px
-}
-
-.navbar .navbar-inner {
-  height: 50px;
+  min-width: 600px;
 }
 
 .navbar .brand {
@@ -46,6 +41,7 @@
 .navbar-text {
   height: 50px;
   line-height: 3.3;
+  white-space: nowrap;
 }
 
 table.sortable thead {

core/src/main/scala/org/apache/spark/ui/UIUtils.scala

@@ -210,10 +210,10 @@ private[spark] object UIUtils extends Logging {
                 <span class="version">{org.apache.spark.SPARK_VERSION}</span>
               </a>
             </div>
-            <ul class="nav">{header}</ul>
             <p class="navbar-text pull-right">
               <strong title={appName}>{shortAppName}</strong> application UI
             </p>
+            <ul class="nav">{header}</ul>
           </div>
         </div>
         <div class="container-fluid">