Metrics - Add actions/README.md

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 6a1fed111695b852f8b8d59161c3155985b7fb3e..5c1bd38431978df83baa1388080a6da21cae048a 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8,9 +8,9 @@ found in the LICENSE file.
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
-For best practices on writing histogram descriptions, see README.md in this
-directory.  For details on how to modify this file to add your description,
-keep reading.
+For best practices on writing histogram descriptions, see
+https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md
+For details on how to modify this file to add your description, keep reading.
 
 Please pretty-print and validate your edits by running the pretty_print.py
 and validate_format.py scripts in the same directory as this file before