Support "await a stable state" and "provide a stable state"

Source/core/html/parser/HTMLScriptRunner.cpp

Index: Source/core/html/parser/HTMLScriptRunner.cpp
diff --git a/Source/core/html/parser/HTMLScriptRunner.cpp b/Source/core/html/parser/HTMLScriptRunner.cpp
index 2d73cce4c81cdda555d589f2690692f29055aef1..8e9e75f251dbccba97d297745f4cc9d6f6aa95d1 100644
--- a/Source/core/html/parser/HTMLScriptRunner.cpp
+++ b/Source/core/html/parser/HTMLScriptRunner.cpp
@@ -28,15 +28,16 @@
 
 #include "bindings/v8/ScriptSourceCode.h"
 #include "core/dom/Element.h"
-#include "core/events/Event.h"
 #include "core/dom/IgnoreDestructiveWriteCountIncrementer.h"
 #include "core/dom/Microtask.h"
 #include "core/dom/ScriptLoader.h"
+#include "core/events/Event.h"
 #include "core/fetch/ScriptResource.h"
+#include "core/frame/Frame.h"
+#include "core/html/StableState.h"
 #include "core/html/parser/HTMLInputStream.h"
 #include "core/html/parser/HTMLScriptRunnerHost.h"
 #include "core/html/parser/NestingLevelIncrementer.h"
-#include "core/frame/Frame.h"
 #include "platform/NotImplemented.h"
 
 namespace WebCore {
@@ -288,8 +289,10 @@ void HTMLScriptRunner::runScript(Element* script, const TextPosition& scriptStar
 
         ASSERT(scriptLoader->isParserInserted());
 
-        if (!isExecutingScript())
+        if (!isExecutingScript()) {
             Microtask::performCheckpoint();
+            StableState::provide();
+        }
 
         InsertionPointRecord insertionPointRecord(m_host->inputStream());
         NestingLevelIncrementer nestingLevelIncrementer(m_scriptNestingLevel);