Handle multiline interpolated strings in line-based scanner.

dart/site/try/src/selection.dart

Index: dart/site/try/src/selection.dart
diff --git a/dart/site/try/src/selection.dart b/dart/site/try/src/selection.dart
index c0d606eb7d11ff4eb01d1c5e731a914b908cadb3..e458bae81b1e5d263c12579a38fb5bbecc96a393 100644
--- a/dart/site/try/src/selection.dart
+++ b/dart/site/try/src/selection.dart
@@ -42,7 +42,12 @@ class TrySelection {
                             [Decoration decoration]) {
     if (start == end) return null;
 
-    Text textNode = new Text(text.substring(start, end));
+    String substring = text.substring(start, end);
+    if (substring == '\n') {
+      // Don't add decorations to trailing newline.
+      decoration = null;
+    }
+    Text textNode = new Text(substring);
 
     if (start <= globalOffset && globalOffset <= end) {
       anchorNode = textNode;