[Extensions] Convert some ChromeSyncExtensionFunctions

extensions/browser/extension_function.cc

Index: extensions/browser/extension_function.cc
diff --git a/extensions/browser/extension_function.cc b/extensions/browser/extension_function.cc
index adbb62df7765cc41f296748a713e1968b6d20bf5..e734dee7e8699e31f7f27ca9e813a853eeb2bc05 100644
--- a/extensions/browser/extension_function.cc
+++ b/extensions/browser/extension_function.cc
@@ -225,6 +225,9 @@ void UserGestureForTests::DecrementCount() {
 bool ExtensionFunction::ignore_all_did_respond_for_testing_do_not_use = false;
 
 // static
+const char* ExtensionFunction::kUnknownErrorDoNotUse = "Unknown error.";
+
+// static
 void ExtensionFunctionDeleteTraits::Destruct(const ExtensionFunction* x) {
   x->Destruct();
 }