NaCl: Update revision in DEPS, 2c9f793 -> 456d6e4

NaCl: Update revision in DEPS, 2c9f793 -> 456d6e4

This pulls in the following Native Client changes:

33b6a18: (yusukes@chromium.org) Implement faster NaClSysFutex functions for NACL_LINUX
0eec380: (yusukes@chromium.org) Revert "Implement faster NaClSysFutex functions for NACL_LINUX"
8dfb438: (bradnelson@google.com) Adding android opt bot to the default trybot list.
c5b278d: (mseaborn@chromium.org) irt.h: Add a comment to document that futexes are process-private
62b6f76: (bradnelson@google.com) Pull in new llvm rev, drop old build flag.
43b8d01: (shyamsundarr@chromium.org) use objdump instead of validator's disassembler in proofs.
10c2124: (jfb@chromium.org) PNaCl: Update LLVM revision in pnacl/COMPONENT_REVISIONS
456d6e4: (yusukes@chromium.org) Implement faster NaClSysFutex functions for NACL_LINUX

BUG=none
TEST=browser_tests and nacl_integration
CQ_EXTRA_TRYBOTS=tryserver.chromium.linux:linux_chromium_dbg_32_ng,linux_arm_compile,linux_nacl_sdk_build

Committed: https://crrev.com/3f9e1aae448aea4ca89c03e51b7e0c6015a3dbbb
Cr-Commit-Position: refs/heads/master@{#317354}

[Mark Seaborn, 2015-02-20 17:39:57]

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

[JF, 2015-02-20 17:53:23]

lgtm ー(￣～￣)ξ

[Mark Seaborn, 2015-02-20 18:03:44]

The CQ bit was checked by mseaborn@chromium.org

[commit-bot: I haz the power, 2015-02-20 18:04:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/942033003/1

[commit-bot: I haz the power, 2015-02-20 18:35:39]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-20 18:36:16]

Patchset 1 (id:??) landed as
https://crrev.com/3f9e1aae448aea4ca89c03e51b7e0c6015a3dbbb
Cr-Commit-Position: refs/heads/master@{#317354}