[MD History] Add UMA stats for switching views and the CBD button.

chrome/browser/resources/md_history/browser_service.js

Index: chrome/browser/resources/md_history/browser_service.js
diff --git a/chrome/browser/resources/md_history/browser_service.js b/chrome/browser/resources/md_history/browser_service.js
index 9052df51067dbf2c7ecc7e8daead1b5a530c4c58..b1f842bdbce9022d4466000b768f1f8f01fc7180 100644
--- a/chrome/browser/resources/md_history/browser_service.js
+++ b/chrome/browser/resources/md_history/browser_service.js
@@ -81,6 +81,20 @@ cr.define('md_history', function() {
     },
 
     /**
+     * @param {Array} args
+     */
+    recordAction: function(args) {
+      chrome.send('metricsHandler:recordAction', args);

[tsergeant, 2016/08/15 07:05:17]

Replace args with a single argument for the action name and package it into an
array in the chrome.send call.

(We know exactly what the recordAction call expects, so there's no reason not to
expand it out and get proper type checking).

[calamity, 2016/08/17 03:15:28]

Done.

+    },
+
+    /**
+     * @param {Array} args
+     */
+    recordHistogram: function(args) {
+      chrome.send('metricsHandler:recordInHistogram', args);

[tsergeant, 2016/08/15 07:05:17]

As above, use specific arguments here rather than an array.

[calamity, 2016/08/17 03:15:29]

Done.

+    },
+
+    /**
      * @param {boolean} successful
      * @private
      */