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

chrome/browser/ui/webui/constrained_web_dialog_delegate_base.cc

Index: chrome/browser/ui/webui/constrained_web_dialog_delegate_base.cc
diff --git a/chrome/browser/ui/webui/constrained_web_dialog_delegate_base.cc b/chrome/browser/ui/webui/constrained_web_dialog_delegate_base.cc
index 1b7244dd14edd6951bcba44fbfb102c7d66ead7c..266e8cb6d1402e2bb73142665019e2c1c1438123 100644
--- a/chrome/browser/ui/webui/constrained_web_dialog_delegate_base.cc
+++ b/chrome/browser/ui/webui/constrained_web_dialog_delegate_base.cc
@@ -9,8 +9,10 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/renderer_preferences_util.h"
 #include "chrome/browser/ui/webui/chrome_web_contents_handler.h"
+#include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/renderer_preferences.h"
 #include "ipc/ipc_message.h"
 #include "ui/web_dialogs/web_dialog_delegate.h"
 #include "ui/web_dialogs/web_dialog_ui.h"
@@ -38,9 +40,15 @@ ConstrainedWebDialogDelegateBase::ConstrainedWebDialogDelegateBase(
   } else {
     web_contents_->SetDelegate(this);
   }
+  content::RendererPreferences* prefs =
+      web_contents_->GetMutableRendererPrefs();
   renderer_preferences_util::UpdateFromSystemSettings(
-      web_contents_->GetMutableRendererPrefs(),
-      Profile::FromBrowserContext(browser_context));
+      prefs, Profile::FromBrowserContext(browser_context));
+  // TODO(wjmaclean): Convert this to use the HostZoomMap for the WebContents
+  // when HostZoomMap moves to StoragePartition.
+  prefs->default_zoom_level = content::HostZoomMap::GetDefaultForBrowserContext(
+                                  browser_context)->GetDefaultZoomLevel();
+
   web_contents_->GetRenderViewHost()->SyncRendererPrefs();
 
   // Set |this| as a delegate so the ConstrainedWebDialogUI can retrieve it.