[Payment Request] Populates country field if country code/name is valid.

ios/chrome/browser/ui/payments/address_edit_mediator.mm

Index: ios/chrome/browser/ui/payments/address_edit_mediator.mm
diff --git a/ios/chrome/browser/ui/payments/address_edit_mediator.mm b/ios/chrome/browser/ui/payments/address_edit_mediator.mm
index 1dc7e724b3f71a0774dbe8a21b59b1f0804cf87e..0ee0c5e19c2643d016daa325e23e2d30b5851919 100644
--- a/ios/chrome/browser/ui/payments/address_edit_mediator.mm
+++ b/ios/chrome/browser/ui/payments/address_edit_mediator.mm
@@ -153,7 +153,7 @@
     if ([regions objectForKey:region]) {
       self.regionField.value = region;
     } else if ([[regions allKeysForObject:region] count]) {
-      DCHECK(1 == [[regions allKeysForObject:region] count]);
+      DCHECK_EQ(1U, [[regions allKeysForObject:region] count]);
       self.regionField.value = [regions allKeysForObject:region][0];
     }
   }
@@ -189,16 +189,23 @@
   }
   _countries = countries;
 
-  // If an address is being edited and it has a valid country code, the selected
-  // country code is set to that value. Otherwise, it is set to the default
-  // country code.
-  NSString* countryCode =
+  // If an address is being edited and it has a valid country code or a valid
+  // country name for the autofill::ADDRESS_HOME_COUNTRY field, the selected
+  // country code is set to the respective country code. Otherwise, the selected
+  // country code is set to the default country code.
+  NSString* country =
       [self fieldValueFromProfile:_address
                         fieldType:autofill::ADDRESS_HOME_COUNTRY];
-  _selectedCountryCode =
-      countryCode && [_countries objectForKey:countryCode]
-          ? countryCode
-          : base::SysUTF8ToNSString(countryModel.GetDefaultCountryCode());
+
+  if ([countries objectForKey:country]) {
+    _selectedCountryCode = country;
+  } else if ([[countries allKeysForObject:country] count]) {
+    DCHECK_EQ(1U, [[countries allKeysForObject:country] count]);
+    _selectedCountryCode = [countries allKeysForObject:country][0];
+  } else {
+    _selectedCountryCode =
+        base::SysUTF8ToNSString(countryModel.GetDefaultCountryCode());
+  }
 }
 
 // Queries the region names based on the selected country code.