chromium: Update all channels to latest versions

Overview of the updated versions:

stable: 48.0.2564.116 -> 49.0.2623.75
beta:   49.0.2623.63  -> 49.0.2623.75
dev:    50.0.2657.0   -> 50.0.2661.11

Stable and beta are now in par because of the release of a major stable
update.

The release addresses 26 security vulnerabilities, the following with an
assigned CVE:

 * CVE-2016-1630: Same-origin bypass in Blink. Credit to Mariusz
                  Mlynski.
 * CVE-2016-1631: Same-origin bypass in Pepper Plugin. Credit to Mariusz
                  Mlynski.
 * CVE-2016-1632: Bad cast in Extensions. Credit to anonymous.
 * CVE-2016-1633: Use-after-free in Blink. Credit to cloudfuzzer.
 * CVE-2016-1634: Use-after-free in Blink. Credit to cloudfuzzer.
 * CVE-2016-1635: Use-after-free in Blink. Credit to Rob Wu.
 * CVE-2016-1636: SRI Validation Bypass. Credit to Ryan Lester and
                  Bryant Zadegan.
 * CVE-2015-8126: Out-of-bounds access in libpng. Credit to
                  joerg.bornemann.
 * CVE-2016-1637: Information Leak in Skia. Credit to Keve Nagy.
 * CVE-2016-1638: WebAPI Bypass. Credit to Rob Wu.
 * CVE-2016-1639: Use-after-free in WebRTC. Credit to Khalil Zhani.
 * CVE-2016-1640: Origin confusion in Extensions UI. Credit to Luan
                  Herrera.
 * CVE-2016-1641: Use-after-free in Favicon. Credit to Atte Kettunen of
                  OUSPG.

The full announcement which also includes the link to the bug tracker
can be found here:

http://googlechromereleases.blogspot.de/2016/03/stable-channel-update.html

Also, the 32bit Chrome package needed for the Flash and Widevine plugins
doesn't exist anymore, because Google has dropped support for 32bit
distros, see here for the announcement:

https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/FoE6sL-p6oU

On our end, we need to fix the patch for the plugin paths to work for
the latest dev channel. The change is very minor, because the
nix_plugin_paths_46.patch only doesn't apply because of an iOS-related
ifdef.

Built and tested on my Hydra at:

https://headcounter.org/hydra/eval/311511



Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Fixes: #13665