Fix a lingering reference to _GAP in chain.dart.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//969933002
diff --git a/CHANGELOG.md b/CHANGELOG.md
index aaa409a..9e31d68 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.2.3
+
+* Fix a crash in `Chain.parse`.
+
 ## 1.2.2
 
 * Don't print the first folded frame of terse stack traces. This frame
diff --git a/lib/src/chain.dart b/lib/src/chain.dart
index 03dbed6..87cc6be 100644
--- a/lib/src/chain.dart
+++ b/lib/src/chain.dart
@@ -128,7 +128,7 @@
   ///
   /// Specifically, this parses the output of [Chain.toString].
   factory Chain.parse(String chain) =>
-    new Chain(chain.split(_GAP).map((trace) => new Trace.parseFriendly(trace)));
+    new Chain(chain.split(_gap).map((trace) => new Trace.parseFriendly(trace)));
 
   /// Returns a new [Chain] comprised of [traces].
   Chain(Iterable<Trace> traces)