Unexpected behavior when renaming member on a class which inherits from a different package

[boasjls]

Summary:
Rename/refactor has some unexpected, and potentially unwanted, behavior when working
with identifiers from a different package.

Specifically, in webstorm, if I have a class Foo that declares a member foo and
inherits from class Bar, where Bar is declared in a different package and declares a member bar,
then I can rename foo to bar such that the renamed foo now shadows the bar identifier from Bar.

This is not otherwise allowed if I declare the class Bar in same package as Foo, and could
potentially change the program semantics.

What steps will reproduce the problem?

1. Create a package project 'awesome' in Webstorm. By default this project
   exports the following class

class Awesome {
  bool get isAwesome => true;
}

2. Create a new simple command line project which imports the 'awesome' package.
   Change the contents of main.dart to the following:

import 'package:awesome/awesome.dart';

class MoreAwesome extends Awesome {
  bool get isNotAwesome => false;
}

main(List<String> args) {
  print(new MoreAwesome().isAwesome);
  print(new MoreAwesome().isNotAwesome);
}

3. Use the rename function on the isNotAwesome identifier and rename it to isAwesome
   What is the expected output? What do you see instead?
   Expected:
   An error should be displayed - Renamed field will shadow getter 'isAwesome'.

Actual:
'isNotAwesome' is renamed to 'isAwesome' and running the program will now yield
the output

    false
    false

where it would previously yield

    true
    false

What version of the product are you using?
Dart SDK-1.15-dev.1.0

This appears to be a change that was introduced in Dart-1.14,
and it has been verified that is does not occur in Dart-1.13.

[scheglov]

I started working on this problem a while ago, but I don't remember whether I was able to reproduce it or not. But I cannot reproduce it now, so probably it was fixed.

Adding a new test for this case.
https://codereview.chromium.org/2204263002

[scheglov]

30b2401