generalize FcFontRenderPrepare supression

generalize FcFontRenderPrepare supression

BUG=skia:

[mtklein, 2015-02-05 15:58:35]

mtklein@google.com changed reviewers:
+ bungeman@google.com, mtklein@google.com

[mtklein, 2015-02-05 15:58:38]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2015-02-05 15:59:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/897953006/1

[commit-bot: I haz the power, 2015-02-05 15:59:33]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-02-05 21:59 UTC

[bungeman-skia, 2015-02-05 16:29:51]

Now I remember why this wasn't this broad before. The one thing we do kinda care
about is that we don't leak the returned FcPattern*. The first thing
FcFontRenderPrepare does is "FcPattern* new = FcPatternCreate();", and we would
like to track that allocation. The rest of what this function does will probably
end up 'lost' to pointer following checkers. I wish FcFontRenderPrepare just
took an mutable FcPattern* and mucked with it instead.

Just so we can track the returned allocation, how about adding

{
    #Same root cause as font_config_bug_2.
    #The 'leak' is a copy of font or pattern values into returned pattern
values.
    font_config_bug_4
    Memcheck:Leak
    fun:*alloc
    ...
    fun:FcValue*
    fun:FcFontRenderPrepare
}

so long as we're not leaking the returned pointer, any leaks are FontConfig's.