[DOCS] Add supported OSs and platforms to the SDK download page.

BUG=none
R=
TEST=none
NOTRY=true
(documentation only change)

Review URL: https://codereview.chromium.org/604833006

Cr-Commit-Position: refs/heads/master@{#297511}

3 files changed, 18 insertions, 4 deletions

diff --git a/native_client_sdk/doc_generated/sdk/download.html b/native_client_sdk/doc_generated/sdk/download.html
index 9045bb9..ea60d8e 100644
--- a/native_client_sdk/doc_generated/sdk/download.html
+++ b/native_client_sdk/doc_generated/sdk/download.html
@@ -47,7 +47,11 @@ not install Xcode, you can download and build an <a class="reference external" h
 To build the program you may also need to download and install <a class="reference external" href="https://github.com/kennethreitz/osx-gcc-installer">gcc</a>.</li>
 <li>On Windows, the Native Client SDK includes a copy of GNU Make.</li>
 </ul>
-<h2 id="versioning"><span id="id3"></span>Versioning</h2>
+<h2 id="platforms"><span id="id3"></span>Platforms</h2>
+<p>Native Client supports several operating systems, including Windows, Linux, OSX,
+and ChromeOS. It supports several architectures including on x86-32, x86-64,
+ARM, and MIPS.</p>
+<h2 id="versions"><span id="versioning"></span>Versions</h2>
 <p>Chrome is released on a six week cycle, and developer versions of Chrome are
 pushed to the public beta channel three weeks before each release. As with any
 software, each release of Chrome may include changes to Native Client and the
diff --git a/native_client_sdk/doc_generated/sitemap.html b/native_client_sdk/doc_generated/sitemap.html
index 4c3ff31..f7baa47 100644
--- a/native_client_sdk/doc_generated/sitemap.html
+++ b/native_client_sdk/doc_generated/sitemap.html
@@ -26,7 +26,8 @@
 <li class="toctree-l1"><a class="reference internal" href="/native-client/sdk/download.html">Download the Native Client SDK</a><ul class="small-gap">
 <li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#overview">Overview</a></li>
 <li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#prerequisites">Prerequisites</a></li>
-<li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#versioning">Versioning</a></li>
+<li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#platforms">Platforms</a></li>
+<li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#versions">Versions</a></li>
 <li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#installing-the-sdk">Installing the SDK</a></li>
 <li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#updating-bundles">Updating bundles</a></li>
 <li class="toctree-l2"><a class="reference internal" href="/native-client/sdk/download.html#help-with-the-naclsdk-utility">Help with the <code>naclsdk</code> utility</a></li>
diff --git a/native_client_sdk/src/doc/sdk/download.rst b/native_client_sdk/src/doc/sdk/download.rst
index a52ea50..d1f2c28 100644
--- a/native_client_sdk/src/doc/sdk/download.rst
+++ b/native_client_sdk/src/doc/sdk/download.rst
@@ -73,10 +73,19 @@ Make
   <https://github.com/kennethreitz/osx-gcc-installer>`_.
 * On Windows, the Native Client SDK includes a copy of GNU Make.
 
+.. _platforms:
+
+Platforms
+---------
+
+Native Client supports several operating systems, including Windows, Linux, OSX,
+and ChromeOS. It supports several architectures including on x86-32, x86-64,
+ARM, and MIPS.
+
 .. _versioning:
 
-Versioning
-----------
+Versions
+--------
 
 Chrome is released on a six week cycle, and developer versions of Chrome are
 pushed to the public beta channel three weeks before each release. As with any