Dart: Lazy observatory asset loading. Option to disable the observatory.

mojo/tools/data/benchmarks

Index: mojo/tools/data/benchmarks
diff --git a/mojo/tools/data/benchmarks b/mojo/tools/data/benchmarks
index b3fe8778e86124c30d993bf2891730cd103116e2..bffe7381f077b633910d506855cba43d0a670241 100644
--- a/mojo/tools/data/benchmarks
+++ b/mojo/tools/data/benchmarks
@@ -29,6 +29,24 @@ benchmarks = [
     ]
   },
   {
+    'name': 'dart init no observatory',
+    'app': 'https://core.mojoapps.io/dart_startup.mojo',
+    'duration': 10,
+    'measurements': [
+      {
+        'name': 'initialize',
+        'spec': 'time_until/Dart/initialized'
+      },
+      {
+        'name': 'accept connection',
+        'spec': 'time_between/Dart/initialized/Dart/connected',
+      }
+    ],
+    'shell-args': [
+      '--args-for=mojo:dart_content_handler --disable-observatory',
+    ]
+  },
+  {
     'name': 'cpp init',
     'app': 'https://core.mojoapps.io/trace_me.mojo',
     'duration': 10,