Introduce ChromeZoomLevelPref, make zoom level prefs independent of profile prefs.

chrome/browser/ui/webui/options/browser_options_handler.cc

Index: chrome/browser/ui/webui/options/browser_options_handler.cc
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.cc b/chrome/browser/ui/webui/options/browser_options_handler.cc
index 330dd20e211805e13677b85f86d296e93fc11e5d..610faf01cc8182a7f72461e577c0dc8ce004fc29 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.cc
+++ b/chrome/browser/ui/webui/options/browser_options_handler.cc
@@ -794,6 +794,8 @@ void BrowserOptionsHandler::PageLoadStarted() {
 void BrowserOptionsHandler::InitializeHandler() {
   Profile* profile = Profile::FromWebUI(web_ui());
   PrefService* prefs = profile->GetPrefs();
+  PrefService* zoom_level_prefs = profile->GetZoomLevelPrefs();
+  DCHECK(zoom_level_prefs);
 
   ProfileSyncService* sync_service(
       ProfileSyncServiceFactory::GetInstance()->GetForProfile(profile));
@@ -851,7 +853,8 @@ void BrowserOptionsHandler::InitializeHandler() {
       base::Bind(&BrowserOptionsHandler::SetupAutoOpenFileTypes,
                  base::Unretained(this)));
   default_zoom_level_.Init(
-      prefs::kDefaultZoomLevel, prefs,
+      prefs::kDefaultZoomLevel,
+      zoom_level_prefs,
       base::Bind(&BrowserOptionsHandler::SetupPageZoomSelector,
                  base::Unretained(this)));
   profile_pref_registrar_.Init(prefs);
@@ -1731,8 +1734,9 @@ void BrowserOptionsHandler::SetupFontSizeSelector() {
 }
 
 void BrowserOptionsHandler::SetupPageZoomSelector() {
-  PrefService* pref_service = Profile::FromWebUI(web_ui())->GetPrefs();
-  double default_zoom_level = pref_service->GetDouble(prefs::kDefaultZoomLevel);
+  double default_zoom_level =
+      content::HostZoomMap::GetDefaultForBrowserContext(
+          Profile::FromWebUI(web_ui()))->GetDefaultZoomLevel();
   double default_zoom_factor =
       content::ZoomLevelToZoomFactor(default_zoom_level);