Reland of Fix FreeList::zapFreedMemory to fail "use-of-uninitialized-value" on MSAN

Reland of Fix FreeList::zapFreedMemory to fail "use-of-uninitialized-value" on MSAN

A CL for fallback font collection[1] broke MSAN bots[2] and was reverted.

Another try to fix[2] also fails on MSAN bots at
FreeList::zapFreeMemory[3]. This patch allows zapFreeMemory to write to
uninitialized memory.

Originally landed[4] and then reverted[5] due to missing support of a
combination of #define symbols.

[1] https://codereview.chromium.org/1241613006/
[2] https://codereview.chromium.org/1244973003/
[3] http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_msan_rel_ng/builds/84
[4] https://codereview.chromium.org/1259893002
[5] https://codereview.chromium.org/1257303003

BUG=514099
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=199724

[kojii, 2015-07-30 06:46:48]

kojii@chromium.org changed reviewers:
+ glider@chromium.org, haraken@chromium.org, sigbjornf@opera.com,
tkent@chromium.org, yutak@chromium.org

[kojii, 2015-07-30 06:46:48]

PTAL.

Sorry reviewers for troublesome, the previous CL had an embarrassing typo
(#ifdef mismatch between .h and .cpp.) Don't know why try bots could not catch
it but it was fixed in this CL.

[haraken, 2015-07-30 06:53:53]

LGTM

[tkent, 2015-07-30 06:55:00]

lgtm

[Alexander Potapenko, 2015-07-30 08:54:58]

LGTM

[kojii, 2015-07-30 10:22:11]

The CQ bit was checked by kojii@chromium.org

[commit-bot: I haz the power, 2015-07-30 10:22:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1260013003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1260013003/20001

[commit-bot: I haz the power, 2015-07-30 10:25:19]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=199724