Implement 'help' command for Observatory debugger.

runtime/observatory/lib/src/elements/debugger.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
 <!-- TODO(turnidge): Use core-icon once core_elements work properly in
      devtools -->
 <polymer-element name="icon-expand-less" noscript>
@@ skipping 215 matching lines @@
 
 <polymer-element name="debugger-console" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
       .console {
         margin: 0px 20px 10px 20px;
       }
       .normal {
         font: normal 14px consolas, courier, monospace;
+        white-space: pre;
         line-height: 125%;
       }
       .bold {
         font: bold 14px consolas, courier, monospace;
+        white-space: pre;
         line-height: 125%;
       }
       .spacer {
         height: 20px;
       }
     </style>
     <div id="consoleText" class="console">
       <!-- Console output is added programmatically here using the 'normal'
            and 'bold' styles. -->
     </div>
   </template>
 </polymer-element>
 
 <polymer-element name="debugger-input" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
       .textBox {
         margin: 20px;
         font: 400 16px consolas, courier, monospace;
         width: 95%;
       }
     </style>
     <input id="textBox" class="textBox" type="text" value="{{ text }}" autofocus>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="debugger.dart"></script>