Add setting to isolate zoom changes by default.

chrome/browser/ui/zoom/chrome_zoom_level_otr_delegate.h

Index: chrome/browser/ui/zoom/chrome_zoom_level_otr_delegate.h
diff --git a/chrome/browser/ui/zoom/chrome_zoom_level_otr_delegate.h b/chrome/browser/ui/zoom/chrome_zoom_level_otr_delegate.h
index 5ea6ff8f800bb02007dccadb90564d30fb9f38c2..8fd2a54ccb4e3b3dfa2a279b5972046f47d8d0e6 100644
--- a/chrome/browser/ui/zoom/chrome_zoom_level_otr_delegate.h
+++ b/chrome/browser/ui/zoom/chrome_zoom_level_otr_delegate.h
@@ -11,22 +11,29 @@
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/zoom_level_delegate.h"
 
+class ChromeZoomLevelPrefs;
+
 namespace zoom {
 class ZoomEventManager;
 }
 
 // This class is a light-weight version of ChromeZoomLevelPrefs and is used
 // to connect an OTR StoragePartition's HostZoomMap to the OTR profile's
-// ZoomEventManager.
+// ZoomEventManager and to provide the parent profile's default zoom scope.
 class ChromeZoomLevelOTRDelegate : public content::ZoomLevelDelegate {
  public:
   ChromeZoomLevelOTRDelegate(
-      base::WeakPtr<zoom::ZoomEventManager> zoom_event_manager);
+      base::WeakPtr<zoom::ZoomEventManager> zoom_event_manager,
+      ChromeZoomLevelPrefs* parent_zoom_level_prefs);
   ~ChromeZoomLevelOTRDelegate() override;
 
   // content::ZoomLevelDelegate
   void InitHostZoomMap(content::HostZoomMap* host_zoom_map) override;
 
+  bool GetIsOriginScopePref() const override;
+  std::unique_ptr<DefaultZoomScopeSubscription>
+  RegisterDefaultZoomScopeCallback(const base::Closure& callback) override;
+
  private:
   // This is a callback function that receives notifications from HostZoomMap
   // when per-host zoom levels change. It is used to update the per-host
@@ -36,6 +43,7 @@ class ChromeZoomLevelOTRDelegate : public content::ZoomLevelDelegate {
   base::WeakPtr<zoom::ZoomEventManager> zoom_event_manager_;
   content::HostZoomMap* host_zoom_map_;
   std::unique_ptr<content::HostZoomMap::Subscription> zoom_subscription_;
+  ChromeZoomLevelPrefs* parent_zoom_level_prefs_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeZoomLevelOTRDelegate);
 };