Fix class hierarchy display

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

Index: runtime/observatory/lib/src/elements/class_tree.html
diff --git a/runtime/observatory/lib/src/elements/class_tree.html b/runtime/observatory/lib/src/elements/class_tree.html
index 5217e61890383a315f2b2561c77bf5251b76d9cd..7f406008dde83ecacdc1f4cfad483743f3729738 100644
--- a/runtime/observatory/lib/src/elements/class_tree.html
+++ b/runtime/observatory/lib/src/elements/class_tree.html
@@ -11,7 +11,7 @@
         border-spacing: 0px;
         width: 100%;
         margin-bottom: 20px
-      vertical-align: middle;
+        vertical-align: middle;
       }
 
       tr {
@@ -21,6 +21,10 @@
       tr:hover {
         background-color: #FAFAFA;
       }
+
+      th {
+        text-align: left;
+      }
     </style>
     <nav-bar>
       <top-nav-menu last="{{ true }}"></top-nav-menu>