Firefox misses offsetX at the parent of the SVG tag.
Set offsetX only if it is undefined
Fix the buggy trigger of tooltips
Group threads into processes.
Merge pull request #9 from ThinkerYzu/fix-minimap-layerX

Firefox misses offsetX at the parent of the SVG tag.
Merge pull request #10 from ThinkerYzu/fix-trigger-tooltip

Fix trigger tooltip
Merge pull request #11 from ThinkerYzu/group-threads-processes

Group threads into processes