[iOS][MF] Adds password related histograms

Bug: 878388
Change-Id: Ia0a6622596753d87888e480401e38f7ef61ae539
Reviewed-on: https://chromium-review.googlesource.com/c/1326013Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606890}

ios/chrome/browser/ui/autofill/manual_fill/password_view_controller.mm

@@ -5,6 +5,7 @@
 #import "ios/chrome/browser/ui/autofill/manual_fill/password_view_controller.h"
 
 #include "base/ios/ios_util.h"
+#include "base/metrics/histogram_macros.h"
 #import "ios/chrome/browser/ui/autofill/manual_fill/action_cell.h"
 #import "ios/chrome/browser/ui/autofill/manual_fill/manual_fill_password_cell.h"
 #import "ios/chrome/browser/ui/table_view/chrome_table_view_styler.h"
@@ -42,8 +43,10 @@ constexpr float PopoverMaxHeight = 250;
 }  // namespace
 
 @interface PasswordViewController ()
+
 // Search controller if any.
 @property(nonatomic, strong) UISearchController* searchController;
+
 @end
 
 @implementation PasswordViewController
@@ -114,6 +117,13 @@ constexpr float PopoverMaxHeight = 250;
 #pragma mark - ManualFillPasswordConsumer
 
 - (void)presentCredentials:(NSArray<ManualFillCredentialItem*>*)credentials {
+  if (self.searchController) {
+    UMA_HISTOGRAM_COUNTS_1000("ManualFallback.PresentedOptions.AllPasswords",
+                              credentials.count);
+  } else {
+    UMA_HISTOGRAM_COUNTS_100("ManualFallback.PresentedOptions.Passwords",
+                             credentials.count);
+  }
   [self presentItems:credentials inSection:CredentialsSectionIdentifier];
 }
 

tools/metrics/histograms/histograms.xml

@@ -42925,6 +42925,25 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="ManualFallback.PresentedOptions.AllPasswords"
+    units="Credentials" expires_after="2019-12-31">
+  <owner>javierrobles@chromium.org</owner>
+  <summary>
+    Tracks the number of credentials presented to the user in the &quot;Use
+    other password...&quot; view in Manual Fallback. This is logged everytime
+    the user opens this view.
+  </summary>
+</histogram>
+
+<histogram name="ManualFallback.PresentedOptions.Passwords" units="Credentials"
+    expires_after="2019-12-31">
+  <owner>javierrobles@chromium.org</owner>
+  <summary>
+    Tracks the number of credentials presented to the user in the Passwords
+    Manual Fallback view. This is logged everytime the user opens this view.
+  </summary>
+</histogram>
+
 <histogram name="Media.AcceleratedCompositingActive" enum="BooleanSuccess">
   <obsolete>
     Deprecated as of July 21, 2014.