Trace.current skips an extra frame in JS.

lib/src/trace.dart

Index: lib/src/trace.dart
diff --git a/lib/src/trace.dart b/lib/src/trace.dart
index 8537b6236109fc3f3db452b2c5f894e4bd851d15..20343ad5a53bbe27829d6f19a1fb00046ba63236 100644
--- a/lib/src/trace.dart
+++ b/lib/src/trace.dart
@@ -81,7 +81,11 @@ class Trace implements StackTrace {
     }
 
     var trace = new Trace.from(StackTrace.current);
-    return new LazyTrace(() => new Trace(trace.frames.skip(level + 1)));
+    return new LazyTrace(() {
+      // JS includes a frame for the call to StackTrace.current, but the VM
+      // doesn't, so we skip an extra frame in a JS context.
+      return new Trace(trace.frames.skip(level + (inJS ? 2 : 1)));
+    });
   }
 
   /// Returns a new stack trace containing the same data as [trace].