[builtins] Move StringIndexOf to a builtin.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 9f549bafb269bfdcbdfc87535589a8f4769697d3..3636890779ba93aeaa3a8e9723673e69d0f04d5a 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -1395,6 +1395,8 @@ 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",