REGRESSION(r171966): Custom elements in async imports don't get upgrade.

Source/core/dom/custom/CustomElementMicrotaskResolutionStep.cpp

Index: Source/core/dom/custom/CustomElementMicrotaskResolutionStep.cpp
diff --git a/Source/core/dom/custom/CustomElementMicrotaskResolutionStep.cpp b/Source/core/dom/custom/CustomElementMicrotaskResolutionStep.cpp
index 32394105d0a78da8505b2379e352602eaea8cbe1..5a6e10fb9ff19de75b737fea9ab25360c114310e 100644
--- a/Source/core/dom/custom/CustomElementMicrotaskResolutionStep.cpp
+++ b/Source/core/dom/custom/CustomElementMicrotaskResolutionStep.cpp
@@ -55,13 +55,12 @@ CustomElementMicrotaskResolutionStep::~CustomElementMicrotaskResolutionStep()
 CustomElementMicrotaskStep::Result CustomElementMicrotaskResolutionStep::process()
 {
     m_context->resolve(m_element.get(), m_descriptor);
-    return CustomElementMicrotaskStep::Continue;
+    return CustomElementMicrotaskStep::ContinueWithRemoving;
 }
 
 #if !defined(NDEBUG)
 void CustomElementMicrotaskResolutionStep::show(unsigned indent)
 {
-    fprintf(stderr, "indent: %d\n", indent);
     fprintf(stderr, "%*sResolution: ", indent, "");
     m_element->outerHTML().show();
 }