Minor Observatory UI tweaks.

runtime/observatory/lib/src/service/object.dart

Index: runtime/observatory/lib/src/service/object.dart
diff --git a/runtime/observatory/lib/src/service/object.dart b/runtime/observatory/lib/src/service/object.dart
index 1c6fc0f68b0e326851d3bc2144851b5cd9e2200f..77599a75bb2c9fc2ec12d846deee48f60cb7c196 100644
--- a/runtime/observatory/lib/src/service/object.dart
+++ b/runtime/observatory/lib/src/service/object.dart
@@ -1951,6 +1951,13 @@ class Library extends ServiceObject with Coverage {
     return isolate._eval(this, expression);
   }
 
+  Script get rootScript {
+    for (Script script in scripts) {
+      if (script.uri == uri) return script;
+    }
+    return null;
+  }
+
   String toString() => "Library($uri)";
 }