In Invoke get JSEntryStub and JSConstructEntryStub directly through roots.

Getting them through stub cache introduces bigger overhead.

These stubs are always present.

R=danno@chromium.org

Review URL: http://codereview.chromium.org/8044029

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9446 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/execution.cc

@@ -88,11 +88,9 @@ static Handle<Object> Invoke(bool construct,
 
   Handle<Code> code;
   if (construct) {
-    JSConstructEntryStub stub;
-    code = stub.GetCode();
+    code = isolate->factory()->js_construct_entry_code();
   } else {
-    JSEntryStub stub;
-    code = stub.GetCode();
+    code = isolate->factory()->js_entry_code();
   }
 
   // Convert calls on global objects to be calls on the global