Let's implement the new smaller highlight cards! Trello: https://trello.com/c/KtffMVhY/185-compact-highlight-cards Mockups: https://mozilla.invisionapp.com/share/5THO85V3M7P#/293931290_Option_1

In addition to the style changes, while working on this with UX (Bryan Bell), we decided to make the following changes: * changed highlights to two rows instead of 3 * fill all the possible/max rows with placeholders instead of just the current row * on narrow screens, we hide the last two highlights (like we do for top sites) * no longer showing file type for downloads * if a link has no image (all downloads), we now show a grey box where the image goes instead of pushing the text to the top

Commits pushed to master at https://github.com/mozilla/activity-stream https://github.com/mozilla/activity-stream/commit/e9b6cf72abd6ac59223f3be5ce86887f9fbf1752 Fix Bug 1459289 - compact cards for highlights https://github.com/mozilla/activity-stream/commit/f18fffe9fef4dd06684656ce33f05bfce78fe148 Merge pull request #4159 from rlr/Bug1459289/compact-highlights Fix Bug 1459289 - compact cards for highlights

Commit pushed to master at https://github.com/mozilla/activity-stream https://github.com/mozilla/activity-stream/commit/fdda2139280fd798002196bf8e71f5a7dc2001af chore(highlights): Update mochitest to check for 2 rows of placeholders (#4167) Followup Bug 1459289 - Compact Highlight Cards

The issue is no longer reproducible on the latest Nightly build on Windows 10 x64, Mac 10.13.3 and Arch Linux x64. All the additional changes mentioned in comment 2 have also been verified.