Introduce background.scripts feature for extension manifests.

chrome/common/extensions/extension_file_util.cc

Index: chrome/common/extensions/extension_file_util.cc
diff --git a/chrome/common/extensions/extension_file_util.cc b/chrome/common/extensions/extension_file_util.cc
index e0912421a7e3077d014681306906c85b851740db..914af0a7b07ce5e9854b9d1ad9d557f6286956ae 100644
--- a/chrome/common/extensions/extension_file_util.cc
+++ b/chrome/common/extensions/extension_file_util.cc
@@ -291,9 +291,11 @@ bool ValidateExtension(const Extension* extension, std::string* error) {
   // Validate background page location, except for hosted apps, which should use
   // an external URL. Background page for hosted apps are verified when the
   // extension is created (in Extension::InitFromValue)
-  if (!extension->background_url().is_empty() && !extension->is_hosted_app()) {
+  if (extension->has_background_page() &&
+      !extension->is_hosted_app() &&
+      extension->background_scripts().empty()) {
     FilePath page_path = ExtensionURLToRelativeFilePath(
-        extension->background_url());
+        extension->GetBackgroundURL());
     const FilePath path = extension->GetResource(page_path).GetFilePath();
     if (path.empty() || !file_util::PathExists(path)) {
       *error =