Add testing section of docs

site/dev/testing/buildbot.md

+Skia Buildbots
+==============
+
+Overview
+--------
+
+Like the Chromium team, the Skia team uses [buildbot](http://trac.buildbot.net/)
+to run continuous builds and tests.
+
+Here is a link to our main status page: https://status.skia.org/
+
+There are also Skia client, compile, Android, and FYI console pages for a detailed
+view of those results: 
+  
+  Externally-facing: http://build.chromium.org/p/client.skia/console
+  
+  Internally-facing: http://chromegw.corp.google.com/i/client.skia/console
+                     http://chromegw.corp.google.com/i/client.skia.internal/console
+                     \(only visible internally\)
+
+Architecture
+------------
+
+The buildbot system consists of these elements: \(see
+http://buildbot.net/buildbot/docs/current/manual/introduction.html#system-architecture
+for more detail\) 
+
+* builder
+
+    * one repeatable build and/or test configuration on a given platform.
+    * each builder maintains its own local checkout of the Skia repo
+    * only one builder is running at any given time on any single buildslave; otherwise,
+       different builders could interfere with each other's performance numbers
+
+* buildbot master
+    
+    * watches for new commits to land in the Skia repository 
+      \(https://skia.googlesource.com/skia\) 
+    * whenever a new commit lands, it tells buildbot slaves to start building and 
+      testing the latest revision 
+    * serves up status pages whenever anybody requests them
+
+* buildslave \(or "buildbot slave"\)
+    
+    * a process on a machine that builds and runs code as directed by the buildbot 
+      master
+    * one or more builders run on each buildslave
+
+* build
+
+    * one run of a particular build/test configuration, at a particular code
+      revision

[borenet, 2015/02/25 18:25:23]

I might slightly modify this to include "builder":  one run of a particular
builder, at a particular code revision

[hcm, 2015/02/26 04:27:33]

Done.

+
+
+Status View
+------------
+
+The buildbot master process watches for new commits to land in the Skia
+repository \(https://skia.googlesource.com/skia\).  Whenever a new commit is
+made, the buildbot master tells slaves to start building and testing the latest
+revision.
+
+If the new commits land faster than the buildbots have time to cycle through all
+buildbot types, then not every revision will be tested individually.  Instead,
+if the commits are on the same branch, they will be batched into a single build.

[borenet, 2015/02/25 18:25:23]

I don't think these first two paragraphs are needed in this section.  The first
is already stated under "buildbot master" above.  If you want to keep the
second, I think we could move it after the following paragraph ("The status
view...").

[hcm, 2015/02/26 04:27:33]

Done.

+
+The status view shows a table with builders, grouped by test type and platform,
+on the X-axis and commits on the Y-axis.  The cells are colored according to
+the status of the build for each commit: green indicates success, red indicates
+failure, light orange indicates an in-progress build, and white indicates that
+no build has started yet for a given revision. Commits are listed by author, and
+the branch on which the commit was made is shown on the very left.
+
+For more detail, you can click on an individual cell to get a summary of the
+steps which ran for that build.  You can also click one of the white bars at
+the top of each column to see a summary of recent builds for a given builder.
+
+
+
+