Test coverage for src/components/header

[gregtatum]

In attempting to uncover our worst offenders for code coverage, the header component stands out.

• [ ] TimeSelectionScrubber (53 lines uncovered)
• [ ] IntervalMarkerOverview (47 lines uncovered)
• [ ] ProfileThreadHeaderContextMenu (26 lines uncovered)
• [ ] SelectionScrubberOverlay (26 lines uncovered)
• [ ] ProfileThreadHeaderBar (25 lines uncovered)
• [ ] ThreadStackGraph (14 lines uncovered)
• [ ] OverflowEdgeIndicator (8 lines uncovered)
• [ ] ProfileThreadJankOverview (6 lines uncovered)
• [x] ProfileViewerHeader (3 lines uncovered)
• [x] TimeRuler (2 lines uncovered)
• [x] EmptyThreadIndicator (0 lines uncovered)
• [x] ProfileThreadTracingMarkerOverview (0 lines uncovered)

┆Issue is synchronized with this Jira Task

[patrykgruszka]

The src/components/header path no longer exists.

These 2 classes have been moved:

• https://app.codecov.io/gh/firefox-devtools/profiler/blob/main/src%2Fcomponents%2Fshared%2Fthread%2FStackGraph.js
• https://app.codecov.io/gh/firefox-devtools/profiler/blob/main/src%2Fcomponents%2Ftimeline%2FOverflowEdgeIndicator.js

[julienw]

I believe the "header" directory moved to "timeline" indeed. For example I believe the two Selection files were merged to https://app.codecov.io/gh/firefox-devtools/profiler/blob/main/src%2Fcomponents%2Ftimeline%2FSelection.js (still needs some coverage)

Other components are missing coverage too, see https://app.codecov.io/gh/firefox-devtools/profiler/tree/main/src%2Fcomponents%2Ftimeline (esp GlobalTrack and LocalTrack, Ruler) due to recent changes that landed without tests.