Add a note to the documentation on assuming your CL not is the culprit.

docs/speed/addressing_performance_regressions.md

Index: docs/speed/addressing_performance_regressions.md
diff --git a/docs/speed/addressing_performance_regressions.md b/docs/speed/addressing_performance_regressions.md
index f012a04a158b05287de73f8d6b0212f80ddb2cc2..e228ef1264981911c1eb1d37e5cad8e55d0f1576 100644
--- a/docs/speed/addressing_performance_regressions.md
+++ b/docs/speed/addressing_performance_regressions.md
@@ -118,6 +118,13 @@ There's a lot of information packed in that bug comment! Here's a breakdown:
 
 ## If you don't believe your CL could be the cause
 
+*** promo

[sullivan, 2017/06/19 16:56:23]

This "promo" block is a gitiles markdown extension:
https://gerrit.googlesource.com/gitiles/+/HEAD/Documentation/markdown.md#Noti...

+Please remember that our performance tests exist to catch unexpected
+regressions. Often, the tests catch performance problems the CL author was
+not aware of. Please look at the data carefully and understand what the test
+is measuring before concluding that your CL is not related.
+***
+
 There are some clear reasons to believe the bisect bot made a mistake:
 
   * Your CL changes a test or some code that isn't compiled on the platform