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

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 cc783b848d0b4883dbfe31779a3ded257ce5dda8..9e31799b6f1baa810002f61380482401ce13fd47 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -18370,6 +18370,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="History.HistoryView" enum="HistoryView">
+  <owner>calamity@chromium.org</owner>
+  <summary>
+    The page of the MD History page shown to the user. Logged each time the user
+    loads the MD History page or switches pages.
+  </summary>
+</histogram>
+
 <histogram name="History.InMemoryDBItemCount">
   <owner>gab@chromium.org</owner>
   <summary>
@@ -81135,6 +81143,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </int>
 </enum>
 
+<enum name="HistoryView" type="int">
+  <int value="0" label="History"/>
+  <int value="1" label="Grouped Week"/>
+  <int value="2" label="Grouped Month"/>
+  <int value="3" label="Synced Tabs"/>
+  <int value="4" label="Signin Promo"/>
+</enum>
+
 <enum name="HotwordAvailability" type="int">
   <int value="0" label="Unavailable -- reason may be unknown"/>
   <int value="1" label="Available"/>