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

native_client_sdk/doc_generated/sdk/release-notes.html

Index: native_client_sdk/doc_generated/sdk/release-notes.html
diff --git a/native_client_sdk/doc_generated/sdk/release-notes.html b/native_client_sdk/doc_generated/sdk/release-notes.html
index a040fc2cdc402975c75ffb8595da6f3e95552988..722461950d29146df69be7f709f4c12269d1d83b 100644
--- a/native_client_sdk/doc_generated/sdk/release-notes.html
+++ b/native_client_sdk/doc_generated/sdk/release-notes.html
@@ -25,6 +25,16 @@ browser (version <code>Y</code>).</li>
 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.</li>
+<li>PNaCl&#8217;s experimental <a class="reference external" href="https://chromium.googlesource.com/native_client/pnacl-subzero/">Subzero translator</a> is available for x86-32 NaCl in
+Chrome version 43, behind a flag. To give it a try, run Chrome with the
+<code>--enable-pnacl-subzero</code> commandline flag, and use the <code>optlevel 0</code>
+<a class="reference internal" href="/native-client/reference/nacl-manifest-format.html#pnacl-nmf-optlevels"><em>NaCl manifest option</em></a>. Application startup time
+should be several times faster than the previous LLVM-based <code>optlevel 0</code>
+mode, with similar code quality. Note that x86-32 NaCl requires a 32-bit
+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 <a class="reference internal" href="/native-client/help.html#forums-list"><em>native-client-discuss or native-client-dev</em></a>.
+We are working on improvements and adding new targets.</li>
 </ul>
 <h2 id="chrome-pepper-42-20-february-2015">Chrome/Pepper 42 (20 February 2015)</h2>
 <h3 id="sdk">SDK</h3>