Trace.current skips an extra frame in JS.

JS traces include a frame for StackTrace.current while VM traces do not.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2067063002 .

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.6.6
+
+* `new Trace.current()` and `new Chain.current()` now skip an extra frame when
+  run in a JS context. This makes their return values match the VM context.
+
 ## 1.6.5
 
 * Really fix strong mode warnings.

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].

lib/src/utils.dart

@@ -2,10 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:path/path.dart' as p;
+
 /// The line used in the string representation of stack chains to represent
 /// the gap between traces.
 const chainGap = '===== asynchronous gap ===========================\n';
 
+// TODO(nweiz): When cross-platform imports work, use them to set this.
+/// Whether we're running in a JS context.
+final bool inJS = p.style == p.Style.url;
+
 /// Returns [string] with enough spaces added to the end to make it [length]
 /// characters long.
 String padRight(String string, int length) {

pubspec.yaml

@@ -7,7 +7,7 @@ name: stack_trace
 #
 # When the major version is upgraded, you *must* update that version constraint
 # in pub to stay in sync with this.
-version: 1.6.6-dev
+version: 1.6.6
 author: "Dart Team <misc@dartlang.org>"
 homepage: https://github.com/dart-lang/stack_trace
 description: >