Bugzilla

*Affected versions**
* 60.9.0esr, 68.1.0esr, 69.0.1, 70.0b9, 71.0a1 (2019-09-23);

**Affected platforms**
* Windows 10, macOS 10.13.6, Ubuntu 18.04;

**Steps to reproduce**
1. Launch Firefox, access any webpage;
2. Open DevTools, Netmonitor and click on any request from the list;
3. Hover over the Respons/Request headers top areas;
additionally:
4. Collapse the sections, re-attempt to hover the mouse over;


**Expected result**
* hover effect would be consistent for these 2 sub-sections;

**Actual result**
* right when the headers section is displayed, hovering over the Response headers area has no hover effect displayed
-- it appears only after clicking on any of the headers bellow; 
* hover effect for Request headers section (collapser) no longer appears if section is collapsed;

**Regression range**
* First bad: build_date: 2017-10-08 changeset: 5eba13f5b3a6ad80decdd8c7b30bff5fa477844f
* Last good: build_date: 2017-10-07 changeset: 71a2dacbbb8ba2f3522432ff7e8fc0151ca591f9
* Pushlog: [URL](https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=71a2dacbbb8ba2f3522432ff7e8fc0151ca591f9&tochange=5eba13f5b3a6ad80decdd8c7b30bff5fa477844f)

**Additional notes**
* attached recording with the potential issue;
* same issue for default theme, more visible with dark theme layout.

**Affected versions**
* 60.9.0esr, 68.1.0esr, 69.0.1, 70.0b9, 71.0a1 (2019-09-23);

**Affected platforms**
* Windows 10, macOS 10.13.6, Ubuntu 18.04;

**Steps to reproduce**
1. Launch Firefox, access any webpage;
2. Open DevTools, Netmonitor and click on any request from the list;
3. Hover over the Respons/Request headers top areas;
additionally:
4. Collapse the sections, re-attempt to hover the mouse over;


**Expected result**
* hover effect would be consistent for these 2 sub-sections;

**Actual result**
* right when the headers section is displayed, hovering over the Response headers area has no hover effect displayed
-- it appears only after clicking on any of the headers bellow; 
* hover effect for Request headers section (collapser) no longer appears if section is collapsed;

**Regression range**
* First bad: build_date: 2017-10-08 changeset: 5eba13f5b3a6ad80decdd8c7b30bff5fa477844f
* Last good: build_date: 2017-10-07 changeset: 71a2dacbbb8ba2f3522432ff7e8fc0151ca591f9
* Pushlog: [URL](https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=71a2dacbbb8ba2f3522432ff7e8fc0151ca591f9&tochange=5eba13f5b3a6ad80decdd8c7b30bff5fa477844f)

**Additional notes**
* attached recording with the potential issue;
* same issue for default theme, more visible with dark theme layout.