Make system tray icons not show up as blurry on KDE

KDE uses 24x24 system tray icons. If a smaller icon is provided, KDE stretches
the icon which makes it look blurry. This CL makes the system tray icons used
by Chrome 24x24 by padding the icons with transparent pixels.

BUG=382487
TEST=Manual

Review URL: https://codereview.chromium.org/716253002

Cr-Commit-Position: refs/heads/master@{#304086}
2 files changed