NaCl: Update revision in DEPS, r8480 -> r8500

NaCl: Update revision in DEPS, r8480 -> r8500

This pulls in the following Native Client changes:

r8481: (robertm) Enable an additional shared lib for the pnacl ld experiments.
r8482: (nfullagar) Build gtest with -Wno-missing-field-initializers.  A recent change in
r8483: (robertm) Do not ignore unresolved symbols during pnacl dynamic links.
r8484: (robertm) Prevent any of "fixedfeaturecpu" tests to be run under pnacl.
r8485: (robertm) Make pnacl drivers work static and PIC
r8486: (dschuff) Add sandboxed translator to arm HW spec run
r8487: (ncbray) Make the browser tester use the real IP of the machine it is running on.
r8488: (robertm) Add a step for PIC mode testing to the pnacl toolchain testers.
r8489: (robertm) Make the pnacl shared linking experiment work completely without glibc
r8490: (robertm) Enable pic test for real
r8491: (khim) Add few more CPU-detectable bits to nacl_cpuid.[ch]
r8492: (robertm) Make the pnacl dynamic loader experiment call into the ld.so.
r8493: (dschuff) Don't use slash in buildbot step name; it causes the stdio output URL to be wrong on the web interface.
r8494: (kschimpf) Make default table rows explicit.
r8495: (ncbray) Browser tester: dump entire net log if no URLs are loaded.
r8496: (khim) Disable mach_forward_untrusted_caught_test on coverage bot
r8497: (kschimpf) Remove "x not y" implicit relationships from the table and make explicit!
r8498: (robertm) Roll toolchain deps to rev 8495	
*r8500: (mseaborn) Exception handling: Windows: Add "const" in some places

* The change r8500 above requires a small const fix.

BUG=none
TEST=nacl_integration

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=135604

[Nick Bray (chromium), 2012-05-04 19:19:51]

LGTM