NaCl: Update revision in DEPS, r12790 -> r12794

This pulls in the following Native Client changes:

r12791: (bradnelson) Invoke the compiler to locate the mig definitions files.
r12792: (teravest) Remove unused NACL_MANIFEST_UNREF message.
r12793: (mcgrathr) Update x86 toolchains in TOOL_REVISIONS
r12794: (noelallen) Re-order bionic build to support libc++.so.

BUG=none
TEST=browser_tests and nacl_integration

Review URL: https://codereview.chromium.org/174763002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252853 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252854 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252854