Apply default wallpaper from customization manifest.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index cdf3cae27531426a01e66817fc1a77a4bb9b2757..1737ee9c296d904230c3c25c8379e8e7e36cc662 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -2170,6 +2170,12 @@ const char kUsedPolicyCertificates[] = "policy.used_policy_certificates";
 // after recovery.
 const char kServerBackedDeviceState[] = "server_backed_device_state";
 
+// Customized wallpaper URL, which is already downloaded and scaled.
+// The URL from this preference must never be fetched. It is compared to the
+// URL from customization document to check if wallpaper URL has changed
+// since wallpaper was cached.
+const char kCustomizationDefaultWallpaperURL[] =
+    "customization.default_wallpaper_url";
 #endif
 
 // Whether there is a Flash version installed that supports clearing LSO data.