[Soup] Work around a glib bug
https://bugs.webkit.org/show_bug.cgi?id=106789

Reviewed by Martin Robinson.

In glib <= 2.35.4, g_input_stream_skip_async() applied to a
libsoup response stream will do a synchronous skip() in another
thread, which libsoup isn't expecting and doesn't have proper
locking for. Work around this until the next time we bump the glib
requirement by using read_async() (and throwing away the result)
instead of skip_async().

No new tests; fixes a race condition in existing tests with older
glib

* platform/network/soup/ResourceHandleSoup.cpp:
(WebCore::redirectSkipCallback):
(WebCore::sendRequestCallback):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140338 268f45cc-cd09-0410-ab3c-d52691b4dbfc