First part to fix Bug 50726 "Save extension list and "winning" prefs from extensions"

chrome/browser/extensions/extension_prefs.cc

Index: chrome/browser/extensions/extension_prefs.cc
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index bf80550c19dc12b8f73e0b45464852889ca3dc5d..785a26ebae7621c32e3e807065a7b3c199559fbe 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -41,6 +41,11 @@ const char kExtensionDidEscalatePermissions[] = "install_warning_on_enable";
 // object stored in the Preferences file. The extensions are stored by ID.
 const char kExtensionToolbar[] = "extensions.toolbar";
 
+// An ordered list of extension IDs that determines which extension overwrites
+// the values of other extensions. The last extension wins.
+// The ExtensionPrefStore reads and writes this list to respect the precedences.
+const char kExtensionsPrecedence[] = "extensions.precedence";
+
 // The key for a serialized Time value indicating the start of the day (from the
 // server's perspective) an extension last included a "ping" parameter during
 // its update check.
@@ -209,6 +214,39 @@ DictionaryValue* ExtensionPrefs::CopyCurrentExtensions() {
   return new DictionaryValue;
 }
 
+void ExtensionPrefs::PersistExtensionPrecedences(
+      const std::vector<std::string>& precedence) {
+  ListValue* stored_precedence =
+      pref_service()->GetMutableList(kExtensionsPrecedence);
+
+  stored_precedence->Clear();
+
+  std::vector<std::string>::const_iterator i;
+  for (i = precedence.begin(); i != precedence.end(); ++i)
+    stored_precedence->Append(Value::CreateStringValue(*i));
+  pref_service()->ScheduleSavePersistentPrefs();
+}
+
+void ExtensionPrefs::GetExtensionPrecedences(
+      std::vector<std::string>* precedence) const {
+  precedence->clear();
+
+  const ListValue* stored_precedence =
+      pref_service()->GetList(kExtensionsPrecedence);
+  if (stored_precedence) {
+    precedence->reserve(stored_precedence->GetSize());
+    for (ListValue::const_iterator i = stored_precedence->begin();
+         i != stored_precedence->end(); ++i) {
+      std::string ext_id;
+      if (!(*i)->GetAsString(&ext_id)) {
+        LOG(WARNING) << "Invalid entry in " << kExtensionsPrecedence;
+        continue;
+      }
+      precedence->push_back(ext_id);
+    }
+  }
+}
+
 bool ExtensionPrefs::ReadBooleanFromPref(
     DictionaryValue* ext, const std::string& pref_key) {
   if (!ext->HasKey(pref_key)) return false;
@@ -905,4 +943,5 @@ void ExtensionPrefs::RegisterUserPrefs(PrefService* prefs) {
   prefs->RegisterListPref(prefs::kExtensionInstallDenyList);
   prefs->RegisterListPref(prefs::kExtensionInstallForceList);
   prefs->RegisterStringPref(kWebStoreLogin, std::string() /* default_value */);
+  prefs->RegisterListPref(kExtensionsPrecedence);
 }