message: docs(ivy): document breaking changes for DebugElement classes and attributes
  PR Close
diff: @@ -57,3 +57,7 @@ If the errors are gone, switch back to Ivy by removing the changes to the `tscon
  * ICU parsing happens at runtime, so only text, HTML tags and text bindings are allowed inside ICU cases (previously, directives were also permitted inside ICUs).
  * Providers formatted as `{provide: X}` without a `useValue`, `useFactory`, `useExisting`, or `useClass` property are treated like `{provide: X, useClass: X}` (previously, it defaulted to `{provide: X, useValue: undefined}`).
  +
  +* `DebugElement.attributes` returns `undefined` for attributes that were added and then subsequently removed (previously, attributes added and later removed would have a value of `null`).
  +
  +* `DebugElement.classes` returns `undefined` for classes that were added and then subsequently removed (previously, classes added and later removed would have a value of `false`).
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