NaCl: Update revision in DEPS, r6416 -> r6424

NaCl: Update revision in DEPS, r6416 -> r6424

This pulls in the following Native Client changes:

r6417: (mcgrathr) Make 64-bit syscall trampoline code PIC-friendly
r6418: (mseaborn) Crash dump test: Isolate the test from any global instance of crash_service.exe
r6419: (mseaborn) x86-64 Mac: Fix assembly code to index through %rax rather than %eax
r6420: (khim) Bump REVISION file for GLibC with changed names.
r6421: (jvoung) Update perf expectations for 32-bit pnacl translator compile time.
r6422: (sanga) Adding a check for the number of bytes to write against the buffer size for PPB_FileIO_Write.
r6423: (mcgrathr) Clean up IRT thread creation and exit
r6424: (sanga) Fixing security bug for PPB_FileIO::Read in NaCl proxy.

BUG=none
TEST=trybots

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=96942

[Mark Seaborn, 2011-08-15 23:53:40]

Today's DEPS update.

[Mark Seaborn, 2011-08-16 16:21:02]

Committed TBR.

[bradn, 2011-08-18 17:21:00]

LGTM