Chase imports in analyzer's front_end_inference_test.

pkg/front_end/testcases/inference/infer_from_variables_in_non_cycle_imports_with_flag2.dart.strong.expect

+library test;
+import self as self;
+import "dart:core" as core;
+import "./infer_from_variables_in_non_cycle_imports_with_flag2_a.dart" as inf;
+
+class B extends core::Object {
+  static field core::int y = inf::A::x;
+  constructor •() → void
+    : super core::Object::•()
+    ;
+}
+static method test1() → dynamic {
+  inf::A::x = "hi";
+  self::B::y = "hi";
+}
+static method main() → dynamic {}