[Tab Groups Collapse] Add histograms for number of collapsed groups.

Bug: 1018230
Change-Id: I62de1dd2578f5fc738a15ef71fab6ab6b7310dec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2252646Reviewed-by: Connie Wan <connily@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#780097}

chrome/browser/ui/uma_browsing_activity_observer.cc

@@ -110,6 +110,7 @@ void UMABrowsingActivityObserver::LogRenderProcessHostCount() const {
 void UMABrowsingActivityObserver::LogBrowserTabCount() const {
   int tab_count = 0;
   int tab_group_count = 0;
+  int collapsed_tab_group_count = 0;
   int customized_tab_group_count = 0;
   int app_window_count = 0;
   int popup_window_count = 0;
@@ -132,6 +133,9 @@ void UMABrowsingActivityObserver::LogBrowserTabCount() const {
           !tab_group->visual_data()->title().empty()) {
         ++customized_tab_group_count;
       }
+      if (tab_group->visual_data()->is_collapsed()) {
+        ++collapsed_tab_group_count;
+      }
     }
 
     if (browser->window()->IsActive()) {
@@ -175,6 +179,10 @@ void UMABrowsingActivityObserver::LogBrowserTabCount() const {
   UMA_HISTOGRAM_COUNTS_100("TabGroups.UserCustomizedGroupCountPerLoad",
                            customized_tab_group_count);
 
+  // Record how many tab groups are collapsed across all windows.
+  UMA_HISTOGRAM_COUNTS_100("TabGroups.CollapsedGroupCountPerLoad",
+                           collapsed_tab_group_count);
+
   // Record how many windows are open, by type.
   UMA_HISTOGRAM_COUNTS_100("WindowManager.AppWindowCountPerLoad",
                            app_window_count);

tools/metrics/histograms/histograms.xml

@@ -172717,6 +172717,16 @@ should be kept until we use this API.  -->
   </summary>
 </histogram>
 
+<histogram name="TabGroups.CollapsedGroupCountPerLoad" units="groups"
+    expires_after="2020-12-31">
+  <owner>cyan@chromium.org</owner>
+  <owner>chrome-desktop-ui-sea@google.com</owner>
+  <summary>
+    The number of tabs groups that are collapsed in all browsers (counting
+    app-mode windows) when a load completes.
+  </summary>
+</histogram>
+
 <histogram name="TabGroups.SessionsPerGroup" units="sessions"
     expires_after="2021-02-01">
   <owner>yusufo@chromium.org</owner>