folded code stuck the scroll

### Prerequisites

* [x] Put an X between the brackets on this line if you have done all of the following:
* Reproduced the problem in Safe Mode: https://flight-manual.atom.io/hacking-atom/sections/debugging/#using-safe-mode
* Followed all applicable steps in the debugging guide: https://flight-manual.atom.io/hacking-atom/sections/debugging/
* Checked the FAQs on the message board for common solutions: https://discuss.atom.io/c/faq
* Checked that your issue isn't already filed: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aatom
* Checked that there is not already an Atom package that provides the described functionality: https://atom.io/packages

### Description

I have an HTML document with many characters. when folding different parts of the document, the document loses its fluidity.

You can see a video that I recorded of the behavior. in a certain part of the video, you can notice the speed of the scroll between the zone with folded code, and the zone without folded code.

### Steps to Reproduce

*Edit step 2 by @rsese to mention specific lines to fold*

1. save this gist: https://gist.github.com/unluisco/cb6d39da5f33117618dd0ab728219dce
2. open it with atom
3. fold the svg code (lines 18, 29, and 31)
4. scroll it

**Expected behavior:** [What you expect to happen]

I think the scrolling should be fluid

**Actual behavior:** [What actually happens]

the scrolling is stuck.

**Reproduces how often:** [What percentage of the time does it reproduce?]

whenever I fold a lot of code

### Versions

You can get this information from copy and pasting the output of `atom --version` and `apm --version` from the command line. Also, please include the OS and what version of the OS you're running.

Atom : 1.31.2
Electron: 2.0.7
Chrome : 61.0.3163.100
Node : 8.9.3

apm 2.1.1
npm 6.2.0
node 8.9.3 x64
atom 1.31.2
python 2.7.10
git 2.19.1

### Additional Information

Any additional information, configuration or data that might be necessary to reproduce the issue.

this is the video: https://www.dropbox.com/s/b23i0cmzf2hdzem/atom.mp4?dl=0

The issue describes a scrolling performance problem when code is folded in an HTML document. Start by examining the repository's code folding and rendering logic, likely in the core editor components. Reproduce the bug using the provided gist and steps, then profile the scrolling performance to identify bottlenecks. Look for existing tests related to folding or scrolling to understand the expected behavior.

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