Add an example of embedding a Skia Perf graph to the site docs.

site/dev/testing/skiaperf.md

 Skia Perf
 =========
 
 [Skia Perf](https://perf.skia.org) is a web based interface for exploring
 performance data produced by `nanobench` and the code size bot. The data
 includes:
 
   * The nanobench test times in ms.
   * Total memory consumed during a nanobench run.
   * Code size for various symbol types in bytes.
@@ skipping 16 matching lines @@
     ratio(
       ave(fill(filter("name=desk_wowwiki.skp&sub_result=min_ms"))),
       ave(fill(filter("name=desk_wowwiki.skp&sub_result=ops")))
     )
 
 You can also use the data to answer questions like [how many tests were run per commit](https://perf.skia.org/#1878).
 
     count(filter(""))
 
 See Skia Perf for the [full list of functions available](https://perf.skia.org/help).
+
+Embedding
+---------
+
+Once you create a shortcut, which may or may not include calculations, you
+will be presented with the code to embed that graph as an iframe. For example,
+here is an embedding code for showing the ratio of all 565 tests over all 8888
+tests:
+
+    <iframe src='https://perf.skia.org/frame/#4518' width=500 height=300 frameborder=0></iframe>
+
+And the embedded graph appears as:
+
+  <iframe src='https://perf.skia.org/frame/#4518' width=500 height=300 frameborder=0></iframe>
+