[TEST] Forbid reentering ScriptLoader::prepareScript()

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

Index: third_party/WebKit/Source/core/dom/ScriptLoader.cpp
diff --git a/third_party/WebKit/Source/core/dom/ScriptLoader.cpp b/third_party/WebKit/Source/core/dom/ScriptLoader.cpp
index 16c5e50d74c88c5fa276f2fe1e64983009b9733e..5842611d592b99789b232eea1723f8e9f1b8ba29 100644
--- a/third_party/WebKit/Source/core/dom/ScriptLoader.cpp
+++ b/third_party/WebKit/Source/core/dom/ScriptLoader.cpp
@@ -202,6 +202,13 @@ bool ScriptLoader::isScriptTypeSupported(
 // http://dev.w3.org/html5/spec/Overview.html#prepare-a-script
 bool ScriptLoader::prepareScript(const TextPosition& scriptStartPosition,
                                  LegacyTypeSupport supportLegacyTypes) {
+  DCHECK(!m_inPrepareScript);
+  AutoReset<bool> inPrepareScriptScope(&m_inPrepareScript, true);
+
+  DCHECK(!m_willBeParserExecuted);
+  DCHECK(!m_willExecuteWhenDocumentFinishedParsing);
+  DCHECK(!m_readyToBeParserExecuted);
+
   if (m_alreadyStarted)
     return false;