NaCl: Update revision in DEPS, 26c7e6a -> d6d5f6f

This pulls in the following Native Client changes:

95163bf: (stichnot@chromium.org) Update revision for PNaCl
abee7c9: (petarj@mips.com) PNaCl: Update llvm revision in pnacl/COMPONENT_REVISIONS
b44e8dc: (petarj@mips.com) [MIPS] Make $t8 point to the address of TLS pointers
11ff949: (thakis@chromium.org) clang/win: Fix -Wsign-compare warning in platform_impl.cc
f39aa44: (mseaborn@chromium.org) PNaCl: Update llvm revision in pnacl/COMPONENT_REVISIONS: add ConvertToPSO
aebc3c4: (mcgrathr@chromium.org) Update chrome_rev
c4c237c: (erikchen@chromium.org) Back dynamic text regions with a Mach memory region.
6c30fab: (sbc@chromium.org) untrusted.gypi: Remove support for old gcc newlib toolchain
dd69634: (stichnot@chromium.org) Subzero: Add pnacl-translate support for Subzero+NonSFI+x8632.
2d5bba18: (dschuff@chromium.org) [PNaCl Toolchain] Use static libc++ from Chrome toolchain on Mac
bdd3ffa: (dschuff@chromium.org) Revert of [PNaCl Toolchain] Use static libc++ from Chrome toolchain on Mac (patchset #2 id:20001 of https://codereview.chromium.org/1586243003/ )
a52204c: (dschuff@chromium.org) Revert of [PNaCl toolchain] Stop building and using custom libc++ for OSX hosts (patchset #2 id:20001 of https://codereview.chromium.org/1572753002/ )
7f31837: (dschuff@chromium.org) PNaCl toolchain: Add 'nostdinc++' to build of host tools against libc++
d8cbca8: (dschuff@chromium.org) Update revision for PNaCl
1ba2a7f: (mseaborn@chromium.org) PNaCl dynamic linking: Add initial test of ConvertToPSO pass
d6d5f6f: (mseaborn@chromium.org) Revert of untrusted.gypi: Remove support for old gcc newlib toolchain (patchset #2 id:20001 of https://codereview.chromium.org/1581193006/ )

Changes: https://chromium.googlesource.com/native_client/src/native_client/+log/26c7e6ae1327a43c948f4666fef9e84fe351ab7c..d6d5f6f2ca4cf89084547b0aaf1829980b37b43f

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

Review URL: https://codereview.chromium.org/1613223002

Cr-Commit-Position: refs/heads/master@{#370731}

DEPS

@@ -87,7 +87,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling NaCl
   # and whatever else without interference from each other.
-  'nacl_revision': '26c7e6ae1327a43c948f4666fef9e84fe351ab7c',
+  'nacl_revision': 'd6d5f6f2ca4cf89084547b0aaf1829980b37b43f',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling dEQP
   # and whatever else without interference from each other.