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 9a1d6d78e7a02158e8f93e82f50b0f97b04f60cc..e0f1315bdf79ebbc38d0fd3ccb6be9772a427905 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.cc
+++ b/chrome/browser/ui/webui/options/browser_options_handler.cc
@@ -798,6 +798,12 @@ void BrowserOptionsHandler::PageLoadStarted() {
 void BrowserOptionsHandler::InitializeHandler() {
   Profile* profile = Profile::FromWebUI(web_ui());
   PrefService* prefs = profile->GetPrefs();
+  chrome::ChromeZoomLevelPrefs* zoom_level_prefs = profile->GetZoomLevelPrefs();
+  DCHECK(zoom_level_prefs);

[battre, 2014/10/08 11:27:10]

Can you please check whether this might fail for the new Windows Guest mode?
IIRC it offers a chrome://settings page but is based on incognito mode.

[wjmaclean, 2014/10/10 14:40:29]

I had to make minor modifications here so the DCHECK wouldn't fire in Guest
mode, but it is OK for Guest mode to not have a zoom level prefs.

+  default_zoom_level_subscription_ =
+      zoom_level_prefs->RegisterDefaultZoomLevelCallback(
+          base::Bind(&BrowserOptionsHandler::SetupPageZoomSelector,
+                     base::Unretained(this)));
 
   ProfileSyncService* sync_service(
       ProfileSyncServiceFactory::GetInstance()->GetForProfile(profile));
@@ -854,10 +860,6 @@ void BrowserOptionsHandler::InitializeHandler() {
       prefs::kDownloadExtensionsToOpen, prefs,
       base::Bind(&BrowserOptionsHandler::SetupAutoOpenFileTypes,
                  base::Unretained(this)));
-  default_zoom_level_.Init(
-      prefs::kDefaultZoomLevel, prefs,
-      base::Bind(&BrowserOptionsHandler::SetupPageZoomSelector,
-                 base::Unretained(this)));
   profile_pref_registrar_.Init(prefs);
   profile_pref_registrar_.Add(
       prefs::kNetworkPredictionOptions,
@@ -1525,7 +1527,8 @@ void BrowserOptionsHandler::HandleDefaultZoomFactor(
     const base::ListValue* args) {
   double zoom_factor;
   if (ExtractDoubleValue(args, &zoom_factor)) {
-    default_zoom_level_.SetValue(content::ZoomFactorToZoomLevel(zoom_factor));
+    Profile::FromWebUI(web_ui())->GetZoomLevelPrefs()->SetDefaultZoomLevelPref(
+        content::ZoomFactorToZoomLevel(zoom_factor));
   }
 }
 
@@ -1782,8 +1785,9 @@ 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);