NaCl: Update revision in DEPS, r12515 -> r12523

This pulls in the following Native Client changes:

r12516: (yyanagisawa) Use goma to build nacl on mac.
r12517: (bradnelson) Adding --emit-signatures option to toolchain_build.
r12518: (mcgrathr) toolchain_build: Refactor package generation to support Canadian cross
r12519: (mseaborn) Fix nacl_secure_random() so that it returns random data
r12520: (mcgrathr) toolchain_build: Use source targets for tarballs
r12521: (petarj) [MIPS] Add missing code for syscall_return_regs_test
r12522: (jfb) Test PNaCl's libc++ with setjmp/longjmp exception handling enabled.
r12523: (teravest) NaCl: Permit C++ streams in NaCl code.

BUG=none
TEST=browser_tests and nacl_integration

Review URL: https://codereview.chromium.org/113123002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240478 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240479 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240479