[ Service ] Fix line numbers in step_through_mixin_from_sdk_test

Fixes dart-lang/sdk#42686

Change-Id: I0b2263560a2a01fa897f8b2a1fe0d5ad4b1a6895
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154561
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

Author: bkonyi

runtime/observatory/tests/service/step_through_mixin_from_sdk_test.dart

@@ -35,19 +35,19 @@ List<String> stops = [];
 List<String> expected = [
   "$file:${LINE + 0}:17", // on "Foo" (in "new Foo()")
   "$file:${LINE + 1}:11", // on "="
-  "list.dart:105:25", // on parameter to "contains"
-  "list.dart:106:23", // on "length" in "this.length"
-  "list.dart:107:16", // on "=" in "i = 0"
-  "list.dart:107:23", // on "<" in "i < length"
-  "list.dart:108:15", // on "[" in "this[i]"
+  "list.dart:124:25", // on parameter to "contains"
+  "list.dart:125:23", // on "length" in "this.length"
+  "list.dart:126:16", // on "=" in "i = 0"
+  "list.dart:126:23", // on "<" in "i < length"
+  "list.dart:127:15", // on "[" in "this[i]"
   "$file:${LINE + 13}:23", // on parameter in "operator []"
   "$file:${LINE + 14}:5", // on "return"
-  "list.dart:108:19", // on "=="
-  "list.dart:109:26", // on "length" in "this.length"
-  "list.dart:109:18", // on "!="
-  "list.dart:107:34", // on "++" in "i++"
-  "list.dart:107:23", // on "<" in "i < length"
-  "list.dart:113:5", // on "return"
+  "list.dart:127:19", // on "=="
+  "list.dart:128:26", // on "length" in "this.length"
+  "list.dart:128:18", // on "!="
+  "list.dart:126:34", // on "++" in "i++"
+  "list.dart:126:23", // on "<" in "i < length"
+  "list.dart:132:5", // on "return"
   "$file:${LINE + 4}:5", // on "print"
   "$file:${LINE + 6}:1" // on ending '}'
 ];