Abort and reschedule if script is not ready during execution time

third_party/WebKit/Source/core/dom/ScriptLoader.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2008 Nikolas Zimmermann <zimmermann@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 872 matching lines @@
 
   // 7. "Decrement the ignore-destructive-writes counter of neutralized doc,
   //     if it was incremented in the earlier step."
   // Implemented as the scope out of IgnoreDestructiveWriteCountIncrementer.
 }
 
 void ScriptLoader::Execute() {
   DCHECK(!will_be_parser_executed_);
   DCHECK(async_exec_type_ != ScriptRunner::kNone);
   DCHECK(pending_script_->IsExternal());
+
+  // If revalidation occurs after the script is scheduled for execution,
+  // the script may not be ready at this point.
+  // Abort execution and reschedule when the script is ready again.
+  if (!pending_script_->IsReady()) {
+    pending_script_->WatchForLoad(this);
+    return;
+  }
+
   bool error_occurred = false;
   Script* script = pending_script_->GetSource(KURL(), error_occurred);
   const bool wasCanceled = pending_script_->WasCanceled();
   DetachPendingScript();
   if (error_occurred) {
     DispatchErrorEvent();
   } else if (!wasCanceled) {
     if (ExecuteScript(script))
       DispatchLoadEvent();
     else
@@ skipping 71 matching lines @@
   //     then abort these steps at this point. The script is not executed.
   return DeprecatedEqualIgnoringCase(event_attribute, "onload") ||
          DeprecatedEqualIgnoringCase(event_attribute, "onload()");
 }
 
 String ScriptLoader::ScriptContent() const {
   return element_->TextFromChildren();
 }
 
 }  // namespace blink