Add warning to Mac that passwords are shared between profiles through the underlying keychain.

chrome/browser/resources/options/personal_options.html

 <div id="personal-page" class="page" hidden>
   <h1 i18n-content="personalPage"></h1>
   <div class="displaytable">
 <if expr="pp_ifdef('chromeos')">
     <section>
       <h3 i18n-content="account"></h3>
       <div>
         <img id='account-picture'
             src='chrome://theme/IDR_LOGIN_DEFAULT_USER'>
         <label>
@@ skipping 61 matching lines @@
         <div class="radio">
           <label>
             <input id="passwords-neversave" type="radio" name="passwords_radio"
                 value="false" pref="profile.password_manager_enabled"
                 metric="Options_PasswordManager">
             <span i18n-content="passwordsNeverSave"></span>
           </label>
         </div>
         <div><button id="manage-passwords" i18n-content="manage_passwords"
             pref="profile.password_manager_enabled"></button></div>
+        <div id="mac-passwords-warning" i18n-content="macPasswordsWarning"
+            hidden></div> 
         <!-- This makes the managed-banner appear when the "pref" is
         configured by the IT administrator. -->
         <input name="password_allow_show_hidden" type="text"
             pref="profile.password_manager_allow_show_passwords" hidden>
       </div>
     </section>
     <section id="autofill-section">
       <h3 i18n-content="autofill"></h3>
       <div>
         <div class="checkbox">
@@ skipping 57 matching lines @@
         </div>
         <div id="themes-gallery-div">
           <a id="themes-gallery" i18n-content="themesGallery"
               i18n-values="href:themesGalleryURL" target="_blank"></a>
         </div>
       </div>
     </section>
 </if>
   </div>
 </div>