[runtime] Remove dead code in Runtime_ToObject

BUG=v8:6921

Change-Id: I8facfcc3ecef094843a86789d3aea75ff6b04b16
Reviewed-on: https://chromium-review.googlesource.com/731382Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48802}

src/runtime/runtime-object.cc

@@ -1038,15 +1038,12 @@ RUNTIME_FUNCTION(Runtime_DefineSetterPropertyUnchecked) {
   return isolate->heap()->undefined_value();
 }
 
-
 RUNTIME_FUNCTION(Runtime_ToObject) {
-  HandleScope scope(isolate);
-  DCHECK_EQ(1, args.length());
-  CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
-  RETURN_RESULT_OR_FAILURE(isolate, Object::ToObject(isolate, object));
+  // Runtime call is implemented in InterpreterIntrinsics and lowered in
+  // JSIntrinsicLowering.
+  UNREACHABLE();
 }
 
-
 RUNTIME_FUNCTION(Runtime_ToPrimitive) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());