[WK2][UNIX] Crash in WebKit::PluginProcessProxy::scanPlugin()

[WK2][UNIX] Crash in WebKit::PluginProcessProxy::scanPlugin()
https://bugs.webkit.org/show_bug.cgi?id=101446

Patch by Christophe Dumez <christophe.dumez@intel.com> on 2012-11-07
Reviewed by Kenneth Rohde Christiansen.

Make sure that the disposition of the SIGCHLD signal is reset to the default
before calling g_spawn_sync(). If the disposition is set to SIG_IGN, then
g_spawn_sync() will not be able to return the exit status of the child
process, our exit failure check will be useless and the following warning
will be printed:

GLib-WARNING **: In call to g_spawn_sync(), exit status of a child process
was requested but SIGCHLD action was set to SIG_IGN and ECHILD was received
by waitpid(), so exit status can't be returned. This is a bug in the
program calling g_spawn_sync(); either don't request the exit status, or
don't set the SIGCHLD action.

This patch also adds a NULL-check for stdOut to avoid crashing in such
case and makes use of String::split() to parse stdOut instead of doing it
manually.

* UIProcess/Plugins/unix/PluginProcessProxyUnix.cpp:
(WebKit::PluginProcessProxy::scanPlugin):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@133755 268f45cc-cd09-0410-ab3c-d52691b4dbfc