Add StartupNotify=true to Linux desktop entry

Startup notification is a mechanism for apps to notify the desktop environment
when they are finished starting [1].  Desktop environments may use this to
eg. animate a progress spinner on an app icon until it's finished starting.

As of r565390 [2], Chrome should correctly send the notification.  To let the
launcher know that Chrome now supports this protocol, advertise it by adding
StartupNotify=true to the desktop entry.

[1] https://developer.gnome.org/integration-guide/stable/startup-notification.html.en
[2] https://chromium.googlesource.com/chromium/src.git/+/0a85ddf22d19c89ca524182b42f938ebf4fa50a0

BUG=732443
R=thestig
CC=mario@endlessm.com

Change-Id: Id37dba4b7272e30316e930f6dc0eb625c7107ba6
Reviewed-on: https://chromium-review.googlesource.com/1108354Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568924}

chrome/installer/linux/common/desktop.template

@@ -106,6 +106,7 @@ Comment[zh_CN]=访问互联网
 Comment[zh_HK]=連線到網際網路
 Comment[zh_TW]=連線到網際網路
 Exec=/usr/bin/@@USR_BIN_SYMLINK_NAME@@ %U
+StartupNotify=true
 Terminal=false
 Icon=@@PACKAGE@@
 Type=Application