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 ca31d830aca36d70e599b96aa566790a7e0c93c6..47996c1f3c264ecadc217c9e85511f75cf911284 100644
--- a/chrome/common/extensions/extension_file_util.cc
+++ b/chrome/common/extensions/extension_file_util.cc
@@ -292,9 +292,11 @@ 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 =