Support column-based breakpoints in the VM and Observatory.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="observatory_element.html">
 
 <polymer-element name="script-inset" extends="observatory-element">
   <template>
     <style>
       a {
         color: #0489c3;
         text-decoration: none;
       }
@@ skipping 21 matching lines @@
         line-height: 125%;
         white-space: pre;
         max-width: 0;
       }
       .currentLine {
         background-color: #fff;
       }
       .currentCol {
         background-color: #6cf;
       }
-      .breakAnnotation {
-        background-color: #e66;
-        color: white;
-      }
-      .hitsNone, .hitsNotExecuted, .hitsExecuted {
+      .hitsCurrent, .hitsNone, .hitsNotExecuted, .hitsExecuted {
         display: table-cell;
         vertical-align: top;
         font: 400 14px consolas, courier, monospace;
         margin-left: 5px;
         margin-right: 5px;
         text-align: right;
         color: #a8a8a8;
       }
+      .hitsCurrent {
+        background-color: #6cf;
+        color: black;
+      }
       .hitsNotExecuted {
         background-color: #faa;
       }
       .hitsExecuted {
         background-color: #aea;
       }
       .noCopy {}
       .emptyBreakpoint, .possibleBreakpoint, .busyBreakpoint, .unresolvedBreakpoint, .resolvedBreakpoint  {
         display: table-cell;
         vertical-align: top;
@@ skipping 15 matching lines @@
         cursor: wait;
       }
       .unresolvedBreakpoint {
         color: white;
         background-color: #cac;
       }
       .resolvedBreakpoint {
         color: white;
         background-color: #e66;
       }
+      .unresolvedBreakAnnotation {
+        color: white;
+        background-color: #cac;
+      }
+      .resolvedBreakAnnotation {
+        color: white;
+        background-color: #e66;
+      }
     </style>
   </template>
 </polymer-element>
 
 
 <polymer-element name="source-inset">
 <template>
   <template if="{{ location != null }}">
     <script-inset script="{{ location.script }}"
                   startPos="{{ location.tokenPos }}"
                   endPos="{{ location.endTokenPos }}"
                   height="{{ height }}"
                   currentPos="{{ currentPos }}"
                   inDebuggerContext="{{ inDebuggerContext }}"
                   variables="{{ variables }}">
     </script-inset>
   </template>
 </template>
 </polymer-element>
 
 <script type="application/dart" src="script_inset.dart"></script>