Update PNaCl deprecation doc for gonacl/chrome devsite

This mirrors the announcement that was sent to native-client-discuss.

Bug: 918374
Change-Id: I2e82c60533a2215bdc08ab6668031cba8e94498d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1750204Reviewed-by: Sam Clegg <sbc@chromium.org>
Commit-Queue: Derek Schuff <dschuff@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686616}

native_client_sdk/doc_generated/migration/index.html

@@ -5,10 +5,21 @@
 <h2 id="p-nacl-deprecation-announcements">(P)NaCl Deprecation Announcements</h2>
 <p>Given the momentum of cross-browser WebAssembly support, we plan to focus our
 native code efforts on WebAssembly going forward and plan to remove support for
-PNaCl in Q2 2019 (except for Chrome Apps). We believe that the vibrant
+PNaCl in Q4 2019 (except for Chrome Apps). We believe that the vibrant
 ecosystem around <a class="reference external" href="http://webassembly.org">WebAssembly</a>
 makes it a better fit for new and existing high-performance
 web apps and that usage of PNaCl is sufficiently low to warrant deprecation.</p>
+<p>As of Chrome 76, PNaCl on the open web has been moved behind an
+<a class="reference external" href="https://github.com/GoogleChrome/OriginTrials/blob/gh-pages/developer-guide.md">Origin Trial</a>
+which is a mechanism for web developers to register and get access to a feature that isn&#8217;t on by default.
+This is usually a new proposed feature but in this case it&#8217;s a feature being deprecated.
+A developer can register on the <a class="reference external" href="https://developers.chrome.com/origintrials/#/view_trial/3553340105995321345">Origin Trial Console</a>
+and receive a token, which can be embedded into a page and will enable the feature without the user needing to use a flag.
+(For more details see the linked guide). The trial is scheduled to last through Chrome 78, approximately until December 2019.
+This change is not intended to affect NaCl or PNaCl in Chrome Apps or extensions, and the "enable-nacl"
+flag in chrome://flags can also be used to enable PNaCl locally for testing
+(this flag also retains its current function of enabling non-PNaCl "native" NaCl on any page).
+</p>
 <p>We also recently announced the deprecation Q1 2018 of
 <a class="reference external" href="https://blog.chromium.org/2016/08/from-chrome-apps-to-web.html">Chrome Apps</a>
 outside of ChromeOS.</p>

native_client_sdk/src/doc/migration/index.rst

@@ -8,11 +8,24 @@ WebAssembly Migration Guide
 
 Given the momentum of cross-browser WebAssembly support, we plan to focus our
 native code efforts on WebAssembly going forward and plan to remove support for
-PNaCl in Q2 2019 (except for Chrome Apps). We believe that the vibrant
+PNaCl in Q4 2019 (except for Chrome Apps). We believe that the vibrant
 ecosystem around `WebAssembly <http://webassembly.org>`_
 makes it a better fit for new and existing high-performance
 web apps and that usage of PNaCl is sufficiently low to warrant deprecation.
 
+As of Chrome 76, PNaCl on the open web has been moved behind an
+`Origin Trial
+<https://github.com/GoogleChrome/OriginTrials/blob/gh-pages/developer-guide.md>`_,
+which is a mechanism for web developers to register and get access to a feature that isn't on by default.
+This is usually a new proposed feature but in this case it's a feature being deprecated.
+A developer can register on the `Origin Trial Console
+<https://developers.chrome.com/origintrials/#/view_trial/3553340105995321345>`_
+and receive a token, which can be embedded into a page and will enable the feature without the user needing to use a flag.
+(For more details see the linked guide). The trial is scheduled to last through Chrome 78, approximately until December 2019.
+This change is not intended to affect NaCl or PNaCl in Chrome Apps or extensions, and the "enable-nacl"
+flag in chrome://flags can also be used to enable PNaCl locally for testing
+(this flag also retains its current function of enabling non-PNaCl "native" NaCl on any page).
+
 We also recently announced the deprecation Q1 2018 of
 `Chrome Apps
 <https://blog.chromium.org/2016/08/from-chrome-apps-to-web.html>`_