Enable (optional) blocking of webrequests in case a PAC script cannot be fetched or is invalid.

chrome/browser/extensions/extension_preference_api.h

Index: chrome/browser/extensions/extension_preference_api.h
diff --git a/chrome/browser/extensions/extension_preference_api.h b/chrome/browser/extensions/extension_preference_api.h
index 31c4452c8e4a50658a32e27f980b9ebdd976f9fe..19325d5aa75f9f28427d0a2ca5c7e78ad96a815c 100644
--- a/chrome/browser/extensions/extension_preference_api.h
+++ b/chrome/browser/extensions/extension_preference_api.h
@@ -50,6 +50,8 @@ class PrefTransformerInterface {
   // Returns the pref store representation in case of success or sets
   // |error| and returns NULL otherwise.
   // The ownership of the returned value is passed to the caller.
+  // TODO(battre): add bool* bad_message to allow terminating the entire
+  // extension in order to simulate the behavior of EXTENSION_FUNCTION_VALIDATE.
   virtual Value* ExtensionToBrowserPref(const Value* extension_pref,
                                         std::string* error) = 0;