[Mac OS X] Troll client interaction with Alt+Tab / Command+Tab

LoL client is a tease.

Steps to reproduce:

1. Queue for a match (e.g. ARAM).
2. Temporarily switch to another application (e.g., Google Chrome).
3. Wait for the match join/leave dialog to begin.

Expected:

The LoL client either stays in the background or forces itself to stay in the foreground.

Observed:

The join/leave dialog foregrounds for less than a second on top of other applications, but it disappears too quickly to click either of its buttons.

Observed in several patches, up to and including patch 5.4, on Mac OS X 10.10.2 Yosemite.