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

chrome/browser/renderer_preferences_util.h

Index: chrome/browser/renderer_preferences_util.h
diff --git a/chrome/browser/renderer_preferences_util.h b/chrome/browser/renderer_preferences_util.h
index 62a24ab9d61783077c8d4bffe59a89d5082ef9cc..16fe502452c9dcd9c0446fc918cd3f100bddd7b4 100644
--- a/chrome/browser/renderer_preferences_util.h
+++ b/chrome/browser/renderer_preferences_util.h
@@ -9,13 +9,15 @@ class Profile;
 
 namespace content {
 struct RendererPreferences;
+class WebContents;
 }
 
 namespace renderer_preferences_util {
 
 // Copies system configuration preferences into |prefs|.
 void UpdateFromSystemSettings(content::RendererPreferences* prefs,
-                              Profile* profile);
+                              Profile* profile,
+                              content::WebContents* web_contents);
 
 }  // namespace renderer_preferences_util