[builtins] Move StringIndexOf to a C++ builtin.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index e5745e400a5f0bf8f51e2ce46ee85b47abf01e07..600d9d1269716b473173189f56b108f89a708684 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1392,6 +1392,8 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
                           1, true);
     SimpleInstallFunction(prototype, "charCodeAt",
                           Builtins::kStringPrototypeCharCodeAt, 1, true);
+    SimpleInstallFunction(prototype, "indexOf",
+                          Builtins::kStringPrototypeIndexOf, 1, false);
     SimpleInstallFunction(prototype, "lastIndexOf",
                           Builtins::kStringPrototypeLastIndexOf, 1, false);
     SimpleInstallFunction(prototype, "localeCompare",