[es6] Set correct length for Reflect.get (should be 2, not 3).

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 86d0a5fcb543a81b01c28ec5b7390f3f1854e3a2..fe1250832acaab4fbf59a468509a78bca7c86868 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2042,7 +2042,7 @@ void Genesis::InitializeGlobal_harmony_reflect() {
   SimpleInstallFunction(reflect, factory->deleteProperty_string(),
                         Builtins::kReflectDeleteProperty, 2, true);
   SimpleInstallFunction(reflect, factory->get_string(),
-                        Builtins::kReflectGet, 3, false);
+                        Builtins::kReflectGet, 2, false);
   SimpleInstallFunction(reflect, factory->getOwnPropertyDescriptor_string(),
                         Builtins::kReflectGetOwnPropertyDescriptor, 2, true);
   SimpleInstallFunction(reflect, factory->getPrototypeOf_string(),