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

Source/core/dom/custom/CustomElementMicrotaskImportStep.h

Index: Source/core/dom/custom/CustomElementMicrotaskImportStep.h
diff --git a/Source/core/dom/custom/CustomElementMicrotaskImportStep.h b/Source/core/dom/custom/CustomElementMicrotaskImportStep.h
index d1d20dac78cad3176d608e33d32675c44f0e881b..d2a03bb8fe75b44f8823b4198d943afd84d3ff6d 100644
--- a/Source/core/dom/custom/CustomElementMicrotaskImportStep.h
+++ b/Source/core/dom/custom/CustomElementMicrotaskImportStep.h
@@ -40,6 +40,7 @@
 namespace WebCore {
 
 class CustomElementMicrotaskQueue;
+class HTMLImportChild;
 
 // Processes the Custom Elements in an HTML Import. This is a
 // composite step which processes the Custom Elements created by
@@ -50,19 +51,24 @@ class CustomElementMicrotaskQueue;
 class CustomElementMicrotaskImportStep : public CustomElementMicrotaskStep {
     WTF_MAKE_NONCOPYABLE(CustomElementMicrotaskImportStep);
 public:
-    static PassOwnPtr<CustomElementMicrotaskImportStep> create(PassRefPtr<CustomElementMicrotaskQueue>);
+    static PassOwnPtr<CustomElementMicrotaskImportStep> create(PassRefPtr<CustomElementMicrotaskQueue>, bool shouldStopProcessing);
     virtual ~CustomElementMicrotaskImportStep();
 
-    // API for HTML Imports
-    void importDidFinish();
+    void importDidLoad(HTMLImportChild*);
+    void importWasDestroyed();
 
 private:
-    CustomElementMicrotaskImportStep(PassRefPtr<CustomElementMicrotaskQueue>);
+    CustomElementMicrotaskImportStep(PassRefPtr<CustomElementMicrotaskQueue>, bool shouldStopProcessing);
 
     // CustomElementMicrotaskStep
     virtual Result process() OVERRIDE FINAL;
 
-    bool m_importFinished;
+#if !defined(NDEBUG)
+    virtual void show(unsigned indent) OVERRIDE;
+#endif
+
+    bool m_shouldStopProcessing;
+    HTMLImportChild* m_importWaitingFinish;
     RefPtr<CustomElementMicrotaskQueue> m_queue;
 };