Revert "[Android] Enable hardware acceleration video decoding for WebRTC"

This reverts commit 1b114b10fef10879a90045c7aceb0fff61d6b709.

It's a walk around of the current P1 crash issue of WebRTC, will reopen
the HW decoding after the fix.

BUG=XWALK-1888
[Android][IAP] Add IAP to permission mapping table

By this, user can use make_apk.py to package their application
with IAP extension with correct permission, for example:

$ python make_apk.py --name=apkname --package=org.xwalk.extensions.iap
--permissions=iap --extensions=...
DEPS.xwalk: Bump Chromium version to include glib mainloop for Ozone

Include changes that will now build glib mainloop on the extension process
(only) when building for Ozone.
[Extensions] Force the GLib main-loop on Linux platform

Many Linux external extensions depends on glib mainloop integration,
mainly for DBus. GLib is the default main loop on Linux Desktop, but
when building if Ozone, you get a Libevent mainloop. This patch
brings GLib back to extension process (only) when building Ozone.

Should not affect anything when building with X11 support.

BUG=XWALK-1331
Merge pull request #1996 from tmpsantos/glib_mainloop

[Extensions] Force the GLib main-loop on Linux platform
Merge pull request #2088 from deqing/iap-permission

[Android] [IAP] Add IAP to permission mapping table
[Android] Remove screenOrientation js file from assets list

It was missed in commit 6144114.
Merge pull request #2085 from xingnan/1888

Revert "[Android] Enable hardware acceleration video decoding for WebRTC...
Merge pull request #2103 from wang16/fix_screen_orientation

[Android] Remove screenOrientation js file from assets list
[Tools] generate_gclient-xwalk.py: Remove custom vars support.

We haven't used that in a very long while, and allows us to simplify the
code a little.
WIP code