Selection.selectRanges selects contents of a non-editable element

[Piotrek Koszuliński]

1. Go to placeholder sample.
2. Select placeholder.
3. Click bold button.
4. Click "strong" in elements path

• Expected: placeholder should be selected with fake selection.
• Actual: selection is anchored inside widget element.

Elements path uses the selection#selectElement method which does nothing more than selectRanges, so the issue is inside selectRanges or in browsers (less likely).

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It also concerns IE8, but even more often. In #10887 we needed to disable two tests:

• ​http://ckeditor4.t/dt/core/style/editor.html?name=test-apply-inline-style-on-non-editable-inline-element---at-non-editable-inline-boundary
• ​http://ckeditor4.t/dt/core/style/editor.html?name=test-remove-inline-style-from-non-editable-inline-element---at-non-editable-inline-boundary