Update Perf docs and add a couple screenshots.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3121
NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=3121

Change-Id: Ic2d1743b2dc42701202ff316277db4c944d969d3
Reviewed-on: https://skia-review.googlesource.com/3121
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>

3 files changed, 15 insertions, 26 deletions

diff --git a/site/dev/testing/Cluster.png b/site/dev/testing/Cluster.png
new file mode 100644
index 0000000000..ebb566b672
--- /dev/null
+++ b/site/dev/testing/Cluster.png
diff --git a/site/dev/testing/Perf.png b/site/dev/testing/Perf.png
new file mode 100644
index 0000000000..8985551ba2
--- /dev/null
+++ b/site/dev/testing/Perf.png
diff --git a/site/dev/testing/skiaperf.md b/site/dev/testing/skiaperf.md
index 03a744ca16..f4b5c40dbc 100644
--- a/site/dev/testing/skiaperf.md
+++ b/site/dev/testing/skiaperf.md
@@ -1,16 +1,23 @@
 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:
+[Skia Perf](https://perf.skia.org) is a Polymer-based web application for
+analyzing and viewing performance metrics produced by Skia's testing
+infrastructure.
 
-  * The nanobench test times in ms.
-  * Total memory consumed during a nanobench run.
-  * Code size for various symbol types in bytes.
+<img src=Perf.png style="margin-left:30px" align="left" width="800"/> <br clear="left">
 
-All of the data can be plotted and also can be [analyzed using k-means
-clustering](https://perf.skia.org/clusters/).
+Skia tests across a large number of platforms and configurations, and each
+commit to Skia generates 240,000 individual values are sent to Perf,
+consisting mostly of performance benchmark results, but also including memory
+and coverage data.
+
+Perf includes tools for analyzing such a large corpus of data, the most
+powerful is [k-means clustering](https://perf.skia.org/clusters/). This tools
+groups large sets of performance metrics together based on how they change
+over time, and highlights sets of metrics that have performance regressions.
+
+<img src=Cluster.png style="margin-left:30px" align="left" width="800"/> <br clear="left">
 
 Calculations
 ------------
@@ -18,10 +25,6 @@ Calculations
 Skia Perf has the ability to perform calculations over the test data
 allowing you to build up interesting queries.
 
-For example, this query displays the [total code size of the library over time](https://perf.skia.org/#1877):
-
-    sum(fill(filter("config=memory&sub_result=bytes")))
-
 This query displays [the ratio of playback time in ms to the number of ops for desk\_wowwiki.skp](https://perf.skia.org/#1876):
 
     ratio(
@@ -35,17 +38,3 @@ You can also use the data to answer questions like [how many tests were run per
 
 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>
-