[Mac] Add Warn Before Quitting to Settings. It's still in the Chrome menu, too.

Bug: 900293
Change-Id: I86b7bab7ce9fb2f332f44f7a825544b7ca4eddd3
Reviewed-on: https://chromium-review.googlesource.com/c/1308760Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604127}

chrome/app/settings_strings.grdp

@@ -576,6 +576,9 @@
     <message name="IDS_SETTINGS_TABS_TO_LINKS_PREF" desc="The documentation string of the 'Tabs to Links' preference">
       Pressing Tab on a webpage highlights links, as well as form fields
     </message>
+    <message name="IDS_SETTINGS_WARN_BEFORE_QUITTING_PREF" desc="The documentation string of the 'Warn Before Quitting' preference which is also available in the Chrome app menu.">
+      Show a warning before quitting with ⌘Q
+    </message>
   </if>
 
   <!-- Common -->

chrome/browser/extensions/api/settings_private/prefs_util.cc

@@ -163,6 +163,8 @@ const PrefsUtil::TypedPrefMap& PrefsUtil::GetWhitelistedKeys() {
 #if defined(OS_MACOSX)
   (*s_whitelist)[::prefs::kWebkitTabsToLinks] =
       settings_api::PrefType::PREF_TYPE_BOOLEAN;
+  (*s_whitelist)[::prefs::kConfirmToQuitEnabled] =
+      settings_api::PrefType::PREF_TYPE_BOOLEAN;
 #endif
 
   // On startup.

chrome/browser/resources/settings/appearance_page/appearance_page.html

@@ -179,6 +179,9 @@
         <settings-toggle-button pref="{{prefs.webkit.webprefs.tabs_to_links}}"
             label="$i18n{tabsToLinks}">
         </settings-toggle-button>
+        <settings-toggle-button pref="{{prefs.browser.confirm_to_quit}}"
+            label="$i18n{warnBeforeQuitting}">
+        </settings-toggle-button>
 </if>
       </neon-animatable>
       <template is="dom-if" route-path="/fonts">

chrome/browser/ui/webui/settings/md_settings_localized_strings_provider.cc

@@ -489,6 +489,7 @@ void AddAppearanceStrings(content::WebUIDataSource* html_source,
 #endif
 #if defined(OS_MACOSX)
     {"tabsToLinks", IDS_SETTINGS_TABS_TO_LINKS_PREF},
+    {"warnBeforeQuitting", IDS_SETTINGS_WARN_BEFORE_QUITTING_PREF},
 #endif
   };
   AddLocalizedStringsBulk(html_source, localized_strings,