Regression(r138728): Causes crashes on the build bots
https://bugs.webkit.org/show_bug.cgi?id=106083

Reviewed by Simon Hausmann.

Update encodeTimingFunction() to encode the x/y members only
if the bezierPreset is set to custom. This is needed because
decodeTimingFunction() only decodes x/y members if the
bezierPreset is set to custom.

This fixes assertion hits on the debug build bots.

* Shared/CoordinatedGraphics/CoordinatedGraphicsArgumentCoders.cpp:
(CoreIPC::encodeTimingFunction):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@138790 268f45cc-cd09-0410-ab3c-d52691b4dbfc