GN: Suppress MSVC "const should be initialized" warning in NaCl code

GN: Suppress MSVC "const should be initialized" warning in NaCl code

Some of the NaCl code uses a perfectly sensible code pattern that the
MSVC compiler misunderstands and issues a warning for.  Suppress that
warning for NaCl code.

BUG=512869
R=dpranke@chromium.org

Committed: https://crrev.com/8379ac5916cb0ef3832c1369fca6d547ed07673b
Cr-Commit-Position: refs/heads/master@{#356712}

[Dirk Pranke, 2015-10-29 00:08:21]

lgtm

[Roland McGrath, 2015-10-29 00:20:23]

The CQ bit was checked by mcgrathr@chromium.org

[commit-bot: I haz the power, 2015-10-29 00:22:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1404343004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1404343004/1

[commit-bot: I haz the power, 2015-10-29 00:56:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-29 00:57:52]

Patchset 1 (id:??) landed as
https://crrev.com/8379ac5916cb0ef3832c1369fca6d547ed07673b
Cr-Commit-Position: refs/heads/master@{#356712}

[Peter Kasting, 2015-10-29 00:57:58]

pkasting@chromium.org changed reviewers:
+ pkasting@chromium.org

[Peter Kasting, 2015-10-29 00:57:59]

Is this how we deal with things on the GYP build?

As the resident Windows warning re-enabler, I'm always keen to avoid adding more
suppressions, but especially if they differ between GYP and GN.