[iOS][MF] Add histograms

Adds histograms for:
How many autofill suggestions exists when a user opens passwords manual fallback.
How many autofill suggestions exists when a user opens credit cards manual fallback.
How many autofill suggestions exists when a user opens profiles manual fallback.

Bug: 905653, 845472
Change-Id: I114fee74ea1f78a8fe08b3e8a373fa8946e0d7ae
Reviewed-on: https://chromium-review.googlesource.com/c/1352166
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612166}

ios/chrome/browser/autofill/form_input_accessory_view_controller.mm

@@ -5,6 +5,7 @@
 #import "ios/chrome/browser/autofill/form_input_accessory_view_controller.h"
 
 #include "base/mac/foundation_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "components/autofill/core/common/autofill_features.h"
 #import "ios/chrome/browser/autofill/form_input_accessory_view.h"
 #import "ios/chrome/browser/autofill/form_suggestion_view.h"
@@ -417,14 +418,20 @@ CGFloat const kInputAccessoryHeight = 44.0f;
 }
 
 - (void)accountButtonPressed:(UIButton*)sender {
+  UMA_HISTOGRAM_COUNTS_100("ManualFallback.VisibleSuggestions.OpenProfiles",
+                           self.formSuggestionView.suggestions.count);
   [self.manualFillAccessoryViewControllerDelegate accountButtonPressed:sender];
 }
 
 - (void)cardButtonPressed:(UIButton*)sender {
+  UMA_HISTOGRAM_COUNTS_100("ManualFallback.VisibleSuggestions.OpenCreditCards",
+                           self.formSuggestionView.suggestions.count);
   [self.manualFillAccessoryViewControllerDelegate cardButtonPressed:sender];
 }
 
 - (void)passwordButtonPressed:(UIButton*)sender {
+  UMA_HISTOGRAM_COUNTS_100("ManualFallback.VisibleSuggestions.OpenPasswords",
+                           self.formSuggestionView.suggestions.count);
   [self.manualFillAccessoryViewControllerDelegate passwordButtonPressed:sender];
 }
 

tools/metrics/histograms/histograms.xml

@@ -43993,6 +43993,33 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="ManualFallback.VisibleSuggestions.OpenCreditCards"
+    units="Suggestions" expires_after="2019-12-31">
+  <owner>javierrobles@chromium.org</owner>
+  <summary>
+    Tracks the number of autofill suggestions present when the user taps on the
+    credit card button in manual fallback.
+  </summary>
+</histogram>
+
+<histogram name="ManualFallback.VisibleSuggestions.OpenPasswords"
+    units="Suggestions" expires_after="2019-12-31">
+  <owner>javierrobles@chromium.org</owner>
+  <summary>
+    Tracks the number of password suggestions present when the user taps on the
+    password button in manual fallback.
+  </summary>
+</histogram>
+
+<histogram name="ManualFallback.VisibleSuggestions.OpenProfiles"
+    units="Suggestions" expires_after="2019-12-31">
+  <owner>javierrobles@chromium.org</owner>
+  <summary>
+    Tracks the number of autofill suggestions present when the user taps on the
+    profiles (address) button in manual fallback.
+  </summary>
+</histogram>
+
 <histogram name="Media.AcceleratedCompositingActive" enum="BooleanSuccess">
   <obsolete>
     Deprecated as of July 21, 2014.