x11: Make the event-source work with both glib and libevent message-pumps.

x11: Make the event-source work with both glib and libevent message-pumps.

Split up the X11EventSource into X11EventSourceGlib to work with the glib message-pump,
and X11EventSourceLibevent to work with the libevent message-pump. With this change, it
is possible to build and run chromeos without glib (use_glib = 0).

BUG=354062, 240715
R=darin@chromium.org, sky@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=265007

[sadrul, 2014-04-19 19:17:44]

sky@: Please review chrome/ and ui/ changes.

darin@: please review base/ changes. Do you know who would be a good person to
talk to about message-pump in nacl? The various OS_NACL related #ifdefs in
message_loop.cc|h are fairly confusing, and I would like to make this a bit more
readable where possible.

[darin (slow to review), 2014-04-20 21:24:26]

LGTM for base/

I think OS_NACL just really wants to use the default message pump for
everything, as NaCl doesn't have a (e)poll syscall. You might ask for
clarification of what OS_NACL needs on pepper-dev@.

[sky, 2014-04-21 15:51:08]

LGTM

[sadrul, 2014-04-21 16:24:31]

Committed patchset #5 manually as r265007 (presubmit successful).