NaCl: Update revision in DEPS, r7919 -> r7946

NaCl: Update revision in DEPS, r7919 -> r7946

This pulls in the following Native Client changes:

r7920: (ncbray) Add validation caching interface.
r7921: (jvoung) Change pnacl-nmf "open" calls to "DriverOpen".
r7922: (bradnelson) Passing more information to untrusted crash handlers.
r7923: (bradnelson) Revert 7922 - Passing more information to untrusted crash handlers.
r7924: (bradnelson) Exception handling: Unset the x86 direction flag for untrusted code
r7925: (bradnelson) Revert r7924, which was committed with the wrong description 
r7926: (jvoung) bump chrome rev in nacl
r7928: (bradnelson) Passing more information to untrusted crash handlers (a retry of r7922)
r7929: (jvoung) Augment pnacl error-checking test to check that the temp files are cleaned
r7930: (mseaborn) Fix presubmit errors on mmap_test.cc
r7931: (mcgrathr) Link sel_ldr as PIE under Gyp
r7932: (robertm) Update trusted arm TC
r7934: (sehr) Second attempt at SelLdrLauncher refactoring
r7935: (robertm) Add a new scons variabe "pnacl_stop_with_pexe" which will prevent pnacl from
r7936: (robertm) Update arm trusted TC with additional packages to support recent chrome builds
r7937: (mseaborn) mmap: Fix PROT_NONE fill within a 64k page for end-of-file mappings
r7938: (thakis) Remove debug output from nacl_syscall_handlers_gen.py.
r7939: (mseaborn) mmap_test: Fix test failure under ASan
r7940: (jvoung) Remove extra extern "C" that was in callconv_case_by_case test.
r7941: (thakis) Let build_nexe print nothing in the happy case.
r7942: (mseaborn) Debug stub: Extend test to work on x86-32
r7943: (pdox) Add libelf to the PNaCl build.
r7944: (bradchen) whitespace change to trigger build.
r7945: (pdox) PNaCl libelf build: Add more supplemental header files and patches for compiling on Mac.
r7946: (pdox) Minor tweaks to libelf to get it building on Windows.

BUG=none
TEST=nacl_integration

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=124909

[Nick Bray (chromium), 2012-03-04 21:34:33]

LGTM