NaCl: Update revision in DEPS, 87d5dd9 -> 6937d61

NaCl: Update revision in DEPS, 87d5dd9 -> 6937d61

This pulls in the following Native Client changes:

4699f0e: (sbc@chromium.org) Always honor NACL_TMPFS_PREFIX in the environement
0178d59: (sbc@chromium.org) Add runtime test for availability of PROT_EXEC with shm_open
772dc1f: (dschuff@chromium.org) PNaCl: Update compiler-rt revision in pnacl/COMPONENT_REVISIONS
7408e00: (petarj@mips.com) PNaCl: Update binutils revision in pnacl/COMPONENT_REVISIONS
6937d61: (dschuff@chromium.org) Update revision for PNaCl

Changes: https://chromium.googlesource.com/native_client/src/native_client/+log/87d5dd90911a0657c27574f78e86b7dfc4ad8b29..6937d61627c025d697f70b5a09d02f192a71e157

BUG= https://code.google.com/p/nativeclient/issues/detail?id=4155
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/2cc92c9db0c57e46d4420c7fdec92d620a2b9cb1
Cr-Commit-Position: refs/heads/master@{#327327}

[Derek Schuff, 2015-04-28 16:10:46]

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

[binji, 2015-04-28 16:56:21]

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

[binji, 2015-04-28 16:56:21]

rubber stamp lgtm

[Derek Schuff, 2015-04-28 16:56:41]

The CQ bit was checked by dschuff@chromium.org

[commit-bot: I haz the power, 2015-04-28 16:57:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1109153003/1

[Sam Clegg, 2015-04-28 17:53:53]

On 2015/04/28 16:57:11, I haz the power (commit-bot) wrote:
> CQ is trying da patch. Follow status at
>  https://chromium-cq-status.appspot.com/patch-status/1109153003/1

Please go ahead and land without the win_nacl_sdk_build bot passing.  There is a
separate issue that is causing it to fail.

[commit-bot: I haz the power, 2015-04-28 18:14:47]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-28 18:15:30]

Patchset 1 (id:??) landed as
https://crrev.com/2cc92c9db0c57e46d4420c7fdec92d620a2b9cb1
Cr-Commit-Position: refs/heads/master@{#327327}