NaCl: Update revision in DEPS, r13903 -> r13915

NaCl: Update revision in DEPS, r13903 -> r13915

This pulls in the following Native Client changes:

r13908: (mseaborn) Scons: Stop scanning for multiple versions of ARM GCC
r13909: (mseaborn) ARM: Remove Scons support for using ARM soft-float toolchains
r13910: (bradnelson) Adding a prefix to distinct perf results so they are graphed separately.
r13913: (mazda) Make PNaCl translator use hard-float ABI for ARM nonsfi target.
r13914: (teravest) Add NaClDescCreateWithFilePathMetadata fallback.
r13915: (mseaborn) Clean up sysconf() test to address a TODO that depended on a toolchain roll

BUG=none
TEST=browser_tests and nacl_integration
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:linux_rel_precise32,linux_nacl_sdk,linux_chromium_dbg

Committed: https://crrev.com/db5715789ecc4c18331402717f3d1c60af3fac2d
Cr-Commit-Position: refs/heads/master@{#299818}

[Mark Seaborn, 2014-10-15 22:30:21]

mseaborn@chromium.org changed reviewers:
+ dschuff@chromium.org

[Derek Schuff, 2014-10-15 23:29:20]

lgtm

[Mark Seaborn, 2014-10-15 23:30:01]

The CQ bit was checked by mseaborn@chromium.org

[commit-bot: I haz the power, 2014-10-15 23:31:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/644493004/1

[commit-bot: I haz the power, 2014-10-16 02:03:18]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-16 02:03:47]

Patchset 1 (id:??) landed as
https://crrev.com/db5715789ecc4c18331402717f3d1c60af3fac2d
Cr-Commit-Position: refs/heads/master@{#299818}