Line Height is not reduced after reducing the font size

[rishi]

1. Type "abcdef" in the CK Editor and set the font size to 72.
2. The "abcdef" and paste it in next line.

Now in the source will be "<p><span style="font-size:72px">asdsadsadasd</span></p>"

3. Now select only "abc" change the font size to 8.

At this time source will be

<p><span style="font-size:72px"><span style="font-size:8px">abc</span>def</span></p>

4. Now, select "def" and change the font size also to 8

At this time source will be

<p><span style="font-size:72px"><span style="font-size:8px">abcdef</span></span></p>

Expected: span

<span style="font-size:72px">

tag shuld be deleted in step 4.

Due this the line hieght is set to 72 px. This should be fixed.