Provide Copy button for username in password settings

ios/chrome/app/strings/ios_strings.grd

Index: ios/chrome/app/strings/ios_strings.grd
diff --git a/ios/chrome/app/strings/ios_strings.grd b/ios/chrome/app/strings/ios_strings.grd
index 1a98919b24df565641debfb1301fd9b1991ef675..25d4b318d5e5c49d70b4a6abbee616da2500438b 100644
--- a/ios/chrome/app/strings/ios_strings.grd
+++ b/ios/chrome/app/strings/ios_strings.grd
@@ -1107,6 +1107,9 @@ Handoff must also be enabled in the General section of Settings, and your device
       <message name="IDS_IOS_SEARCH_ENGINE_SETTING_TITLE" desc="The title for Search Engine selection setting [iOS only]">
         Search Engine
       </message>
+      <message name="IDS_IOS_SETTINGS_USERNAME_COPY_BUTTON" desc="Button that the user can press to copy the username to clipboard. [Length: 12em]">
+        Copy
+      </message>
       <message name="IDS_IOS_SETTINGS_PASSWORD_COPY_BUTTON" desc="Button that the user can press to copy the password to clipboard. [Length: 12em]">
         Copy
       </message>
@@ -1128,6 +1131,9 @@ Handoff must also be enabled in the General section of Settings, and your device
       <message name="IDS_IOS_SETTINGS_PASSWORD_SHOW_BUTTON" desc="Button that the user can press in order to have the password displayed in plain text. [Length: 12em]">
         Show
       </message>
+      <message name="IDS_IOS_SETTINGS_USERNAME_WAS_COPIED_MESSAGE" desc="Confirmation that the username was copied. This is shown alone in an infobar at the bottom of the screen. [Length: 40em]">
+        Your username was copied.
+      </message>
       <message name="IDS_IOS_SETTINGS_PASSWORD_WAS_COPIED_MESSAGE" desc="Confirmation that the password was copied. This is shown alone in an infobar at the bottom of the screen after the user successfully reauthenticates with Touch ID or PIN. [Length: 40em]">
         Your password was copied.
       </message>