browser: linux: x11: use desktop filename as wm class
For modern x11 window manager to map applications (ie .desktop files)
to windows, windows need to have their WM_CLASS property set to the
.desktop filename (modulo lower/upper case).
For Chromium, this is the case. But for Google Chrome stable, this
isn't, as the .desktop filename is google-chrome.desktop, and the
WM_CLASS is set to "google-chrome-stable" (chrome's the binary
filename).
This CL changes GetProgramClassName() to return the .desktop filename
(in the case of google-chrome.desktop, it will be "google-chrome").
BUG=456542
Review URL: https://codereview.chromium.org/
1259773005
Cr-Commit-Position: refs/heads/master@{#341746}