Add GA tag to Sphinx, Doxygen

Change-Id: Idb46509156b132e32c8d033f79d59021d71cdb54

cpp/apidoc/Doxyfile

@@ -1140,7 +1140,7 @@ HTML_HEADER            =
 # that doxygen normally uses.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_FOOTER            =
+HTML_FOOTER            = footer.html
 
 # The HTML_STYLESHEET tag can be used to specify a user-defined cascading style
 # sheet that is used by each HTML page. It can be used to fine-tune the look of

cpp/apidoc/footer.html

@@ -0,0 +1,31 @@
+<!-- HTML footer for doxygen 1.8.14-->
+<!-- start footer part -->
+<!--BEGIN GENERATE_TREEVIEW-->
+<div id="nav-path" class="navpath"><!-- id is needed for treeview function! -->
+  <ul>
+    $navpath
+    <li class="footer">$generatedby
+    <a href="http://www.doxygen.org/index.html">
+    <img class="footer" src="$relpath^doxygen.png" alt="doxygen"/></a> $doxygenversion </li>
+  </ul>
+</div>
+<!--END GENERATE_TREEVIEW-->
+<!--BEGIN !GENERATE_TREEVIEW-->
+<hr class="footer"/><address class="footer"><small>
+$generatedby &#160;<a href="http://www.doxygen.org/index.html">
+<img class="footer" src="$relpath^doxygen.png" alt="doxygen"/>
+</a> $doxygenversion
+</small></address>
+<!--END !GENERATE_TREEVIEW-->
+
+<script async src="https://www.googletagmanager.com/gtag/js?id=UA-107500873-1"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
+
+  gtag('config', 'UA-107500873-1');
+</script>
+
+</body>
+</html>

python/doc/source/_templates/layout.html

@@ -0,0 +1,13 @@
+{# Import the theme's layout. #}
+{% extends "!layout.html" %}
+
+{%- block footer %}
+<script async src="https://www.googletagmanager.com/gtag/js?id=UA-107500873-1"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
+
+  gtag('config', 'UA-107500873-1');
+</script>
+{% endblock %}