Add PNaCl release note about how to try out Subzero / which flag to set.

native_client_sdk/src/doc/sdk/release-notes.rst

Index: native_client_sdk/src/doc/sdk/release-notes.rst
diff --git a/native_client_sdk/src/doc/sdk/release-notes.rst b/native_client_sdk/src/doc/sdk/release-notes.rst
index 2ce371889fecb224fb535de93b16e18726995b9d..ed0da0348caf42c7824aab19d6ec9c14d0f5ae75 100644
--- a/native_client_sdk/src/doc/sdk/release-notes.rst
+++ b/native_client_sdk/src/doc/sdk/release-notes.rst
@@ -33,9 +33,22 @@ PNaCl
   deprecated and will be removed in the next release. PNaCl has used libc++
   (which is much more up-to-date, currently based on LLVM 3.6) as the default
   since Pepper 33.
+* PNaCl's experimental `Subzero translator`_ is available for x86-32 NaCl in
+  Chrome version 43, behind a flag. To give it a try, run Chrome with the
+  ``--enable-pnacl-subzero`` commandline flag, and use the ``optlevel 0``
+  :ref:`NaCl manifest option<pnacl_nmf_optlevels>`. Application startup time
+  should be several times faster than the previous LLVM-based ``optlevel 0``
+  mode, with similar code quality. Note that x86-32 NaCl requires a 32-bit

[jvoung (off chromium), 2015/04/03 22:18:11]

"similar or better?"

+  Chrome. On Windows, it also requires a 32-bit Windows OS, but 64-bit Linux
+  OSes can run x86-32 NaCl. If you try it out, please send us feedback
+  on :ref:`native-client-discuss or native-client-dev<forums_list>`.
+  We are working on improvements and adding new targets.

[JF, 2015/04/03 22:02:10]

Just specify one mailing list to contact, otherwise how do people choose?

[jvoung (off chromium), 2015/04/03 22:18:11]

Semi-arbitrarily picking native-client-dev, since that is lower traffic / needs
some love.

 
 .. _`code generation bug on ARM`: https://code.google.com/p/chromium/issues/detail?id=460432
 
+.. _`Subzero translator`: https://chromium.googlesource.com/native_client/pnacl-subzero/

[JF, 2015/04/03 22:02:10]

Change to:
 
https://chromium.googlesource.com/native_client/pnacl-subzero/+/master/README...
?

[jvoung (off chromium), 2015/04/03 22:18:11]

Done. Much better

+
+
 Chrome/Pepper 42 (20 February 2015)
 ===================================