Created attachment 51493 [details]
In the testcase, the baselines for the "E" and "B" do not line up as they should.
This bug depends on https://bugs.webkit.org/show_bug.cgi?id=40986
Although, the vertical alignment isn't quite what you expecting. The divisor line of the fraction lines up with the middle of the equals. That centers the fraction and aligns the divisor line with the minus sign that precedes it.
I do not understand why "E" and "B" baselines should be aligned by default.
Firefox & Opera behave like WebKit by aligning fraction bar with the equal glyph.
I believe this issue has been resolved with the latest trunk version.