Add comments for the usage of Chrome and Google strings and logos.

ios/chrome/app/strings/ios_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definition of resources that will be translated for each
 locale.  The strings in this file are specific to iOS.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       output_all_resource_defines="false" source_lang_id="en" enc_check="möl">
   <outputs>
@@ skipping 137 matching lines @@
       </message>
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_CONFIRMATION_SERVICES_DESCRIPTION" desc="Description of the Google services section on the sign-in confirmation screen. [Length: unlimited]">
         Google may use your browsing history to personalize Search, ads, and other Google services.
       </message>
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_CONFIRMATION_SERVICES_TITLE" desc="Title of the Google services section on the sign-in confirmation screen. [Length: 50em]">
         Personalize Google services
       </message>
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_CONFIRMATION_SYNC_DESCRIPTION" desc="Description of the Chrome sync section on the sign-in confirmation screen. [Length: unlimited]">
         Your bookmarks, history, passwords, and other settings will be synced to your Google Account so you can use them on all your devices.
       </message>
+      <!-- "Chrome sync" is the Google Cloud Based service used for sync. Thus this string resource is set to "Chrome sync" even for Chromium builds. -->
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_CONFIRMATION_SYNC_TITLE" desc="Title of the Chrome sync section on the sign-in confirmation screen. [Length: 50em]">
         Chrome Sync
       </message>
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_CONFIRMATION_TITLE" desc="Title of the screen confirming selection of an account. [Length: 10em] [iOS only]">
         Hi, <ph name="FULL_ACCOUNT_NAME">$1<ex>Jane Doe</ex></ph>
       </message>
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_CONFIRMATION_UNDO_BUTTON" desc="Title of the button to undo sign-in. [Length: 20em] [iOS only]">
         Undo
       </message>
       <message name="IDS_IOS_ACCOUNT_CONSISTENCY_SETUP_ADD_ACCOUNT_BUTTON" desc="Title of the button to add a new account to the device. [Length: 20em] [iOS only]">
@@ skipping 1337 matching lines @@
       </message>
       <message name="IDS_IOS_VOICE_SEARCH_SETTING_TITLE" desc="The title for Voice Search setting [Length: 29em] [iOS only]">
         Voice Search
       </message>
       <message name="IDS_IOS_VOICE_SEARCH_SETTING_TTS" desc="The label for setting switch enabling text-to-speech response after voice search [Length: 29em] [iOS only]">
         Speak Answers Back
       </message>
     </messages>
   </release>
 </grit>