[Affected versions]: - Firefox 59.0a1 Build ID 20171228220110 [Affected Platforms]: - All Linux [Prerequisites]: - Have enough history so that all 12 Top Sites are populated. [Steps to reproduce]: 1. Start the browser with the profile from prerequisites. 2. Drag and drop a Top Site two positions to the left or right. 3. Observe the behavior. [Expected results]: - The Top Site is moved to the selected location. [Actual results]: - The Top Site is moved only one position to the left or right. [Notes]: - The unpin option does not work for the moved Top Site. - If the same Top Site is moved a second time, it is also duplicated. - After the page is refreshed the Top Site is moved back to its initial location. - Attached a screen recording of the issue.

Some quick debbugging points to dragover events stop after dragging over a different site. Here's the event and props.index from onDragEvent: dragstart 0 dragenter 0 (the current link) dragover 0 (multiple) dragenter 0 dragleave 0 dragover 0 (multiple) Above is dragging but before leaving the initial link. Below is dragging onto another link. dragleave 0 dragenter 0 dragover 0(multiple) dragenter 1 Looks like when we're over another link, new links get rendered triggering new events? Perhaps the state is getting blown away when a new link instance is rendered?

Commits pushed to master at https://github.com/mozilla/activity-stream https://github.com/mozilla/activity-stream/commit/c2427c0552e1bf330df62c122d84166080a91359 Fix Bug 1427361 - linux drag and drop https://github.com/mozilla/activity-stream/commit/93228660eedd41659ad880ab329ebe21eb1ca8f3 Merge pull request #3918 from rlr/Bug1427361/linux-drag-drop Fix Bug 1427361 - linux drag and drop

I have verified that the issue no longer reproducible on the latest Nightly build (20180110100224) on Arch Linux x64, Ubuntu 16.04 x86 and Ubuntu 14.04 x64.