Measure the time spent opening an existing tab

This CL adds a time histogram to measure how long it took for the user
to select an existing time in the tab switcher. If the user opens a new
tab or closes the tab switcher, it is not recorded.

Fixed: 1440186
Change-Id: I1b312978444be13a96796d8665941781dc57738c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4482554
Reviewed-by: Gauthier Ambard <[email protected]>
Reviewed-by: Olivier Robin <[email protected]>
Commit-Queue: Louis Romero <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1136465}

ios/chrome/browser/ui/tab_switcher/tab_grid/tab_grid_view_controller.mm

@@ -194,6 +194,9 @@ @interface TabGridViewController () <DisabledTabViewControllerDelegate,
 // YES if it is possible to undo the close all conditions.
 @property(nonatomic, assign) BOOL undoCloseAllAvailable;
 
+// The timestamp of the user entering the tab grid.
+@property(nonatomic, assign) base::TimeTicks tabGridEnterTime;
+
 @end
 
 @implementation TabGridViewController {
@@ -509,6 +512,9 @@ - (void)contentWillAppearAnimated:(BOOL)animated {
   self.remoteTabsViewController.session = self.view.window.windowScene.session;
 
   self.remoteTabsViewController.preventUpdates = NO;
+
+  // Record when the tab switcher is presented.
+  self.tabGridEnterTime = base::TimeTicks::Now();
 }
 
 - (void)contentDidAppear {
@@ -548,6 +554,8 @@ - (void)contentWillDisappearAnimated:(BOOL)animated {
   [self.regularTabsViewController contentWillDisappear];
   [self.pinnedTabsViewController contentWillDisappear];
   self.remoteTabsViewController.preventUpdates = YES;
+
+  self.tabGridEnterTime = base::TimeTicks();
 }
 
 - (void)dismissModals {
@@ -2203,6 +2211,14 @@ - (void)updateToolbarsAppearance {
   [self.bottomToolbar setScrollViewScrolledToEdge:gridScrolledToBottom];
 }
 
+- (void)reportTabSelectionTime {
+  CHECK(!self.tabGridEnterTime.is_null());
+  base::TimeDelta duration = base::TimeTicks::Now() - self.tabGridEnterTime;
+  base::UmaHistogramLongTimes("IOS.TabSwitcher.TimeSpentOpeningExistingTab",
+                              duration);
+  self.tabGridEnterTime = base::TimeTicks();
+}
+
 #pragma mark UIGestureRecognizerDelegate
 
 - (BOOL)gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer
@@ -2399,6 +2415,9 @@ - (void)thumbStripDisabled {
 - (void)pinnedTabsViewController:
             (PinnedTabsViewController*)pinnedTabsViewController
              didSelectItemWithID:(NSString*)itemID {
+  // Record how long it took to select an item.
+  [self reportTabSelectionTime];
+
   [self.pinnedTabsDelegate selectItemWithID:itemID];
 
   self.activePage = self.currentPage;
@@ -2491,6 +2510,8 @@ - (void)gridViewController:(GridViewController*)gridViewController
           base::UserMetricsAction("MobileTabGridOpenIncognitoTabSearchResult"));
     }
   }
+  // Record how long it took to select an item.
+  [self reportTabSelectionTime];
 
   alreadySelected = [tabsDelegate isItemWithIDSelected:itemID];
   if (!alreadySelected) {

tools/metrics/histograms/metadata/ios/histograms.xml

@@ -2347,6 +2347,17 @@ [email protected].
   </summary>
 </histogram>
 
+<histogram name="IOS.TabSwitcher.TimeSpentOpeningExistingTab" units="ms"
+    expires_after="2024-05-14">
+  <owner>[email protected]</owner>
+  <owner>[email protected]</owner>
+  <owner>[email protected]</owner>
+  <summary>
+    The time it takes for a user to open an existing tab. If the user opens a
+    new tab or closes the tab switcher, this is not recorded.
+  </summary>
+</histogram>
+
 <histogram name="IOS.TabSwitcher.TimeSpentScrolling" units="ms"
     expires_after="2024-05-14">
   <owner>[email protected]</owner>