[GCM] Add experiment and startup logic for partial rollout

The experiment controls whether the GCMProfileService should be suppressed
or force created at sync startup time. If no experiment is present, the default
is for Canary/Dev clients to be able to enable the GCMProfileService lazily,
and other clients to be unable to create it at all.

BUG=284553

Review URL: https://codereview.chromium.org/152633006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249871 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249871
Build the PNaCl IRT shim with PNaCl + NaCl DEPS bump r12710 -> r12726

The ARM one is completely identical (already built with
PNaCl), the x86-32 version is a bit smaller, and the x86-64
one is a bit bigger.

Drops a PNaCl dependency on GCC.

Pull in untrusted.gypi change w/ NaCl DEPS bump r12710 -> r12716

This pulls in the following Native Client changes:

r12711: (bradnelson) Don't write out .pyc files on the bots.
r12712: (halyavin) Fix handle leak in SimpleRevConnection objects.
r12713: (halyavin) Fix bots failures.
r12714: (yyanagisawa) Make try-except for finding gomacc more explicit.
r12715: (halyavin) Fix incorrect code that causes use-after-free.
r12716: (jvoung) Replace force_arm_pnacl w/ pnacl_native_biased and allow building nlibs.
r12717: (mcgrathr) toolchain_build: Update gdb to 7.7 release
r12718: (noelallen) Add bionic upload
r12719: (dschuff) toolchain_build_pnacl: Add support for cmake, clang, and sanitizers
r12720: (jvoung) PNaCl: Update Clang revision in pnacl/COMPONENT_REVISIONS
r12721: (mseaborn) Remove old sel_main_chrome.h/nacl_chrome.h interface variants
r12722: (jvoung) Add a couple more mnemonics to pnacl-ld (-u, --trace, --library, etc.)
r12723: (dschuff) PNaCl driver: use module-splitting by default for offline translation.
r12724: (dyen) IRT TLS now depends on tls_edit instead of compiling in changes.
r12725: (teravest) NaCl: Remove bad comment in sel_main_chrome.c
r12726: (jvoung) Fix arm rules for pnacl_native_biased in untrusted.gypi.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3784
R=bradnelson@google.com, dschuff@chromium.org

Review URL: https://codereview.chromium.org/137623019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249872 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249873 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249873