Explicitly track the lifecycle of PendingScript.

third_party/WebKit/Source/core/dom/ClassicPendingScript.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ClassicPendingScript_h
 #define ClassicPendingScript_h
 
 #include "bindings/core/v8/ScriptStreamer.h"
 #include "core/dom/ClassicScript.h"
 #include "core/dom/PendingScript.h"
@@ skipping 42 matching lines @@
   bool ErrorOccurred() const override;
   bool WasCanceled() const override;
   void StartStreamingIfPossible(Document*, ScriptStreamer::Type) override;
   KURL UrlForClassicScript() const override;
   void RemoveFromMemoryCache() override;
   void DisposeInternal() override;
 
   void Prefinalize();
 
  private:
+  enum ReadyState {
+    // These states are considered "not ready".
+    kWaitingForResource,
+    kWaitingForStreaming,
+    // These states are considered "ready".
+    kReady,
+    kErrorOccurred,
+  };
+
   ClassicPendingScript(ScriptElementBase*,
                        ScriptResource*,
                        const TextPosition&);
   ClassicPendingScript() = delete;
 
+  // Advances the current state of the script, reporting to the client if
+  // appropriate.
+  void AdvanceReadyState(ReadyState);
+
   void CheckState() const override;
 
   // ScriptResourceClient
   void NotifyFinished(Resource*) override;
   String DebugName() const override { return "PendingScript"; }
   void NotifyAppendData(ScriptResource*) override;
 
   // MemoryCoordinatorClient
   void OnPurgeMemory() override;
 
+  ReadyState ready_state_;
   bool integrity_failure_;
-
   Member<ScriptStreamer> streamer_;
 
   // This is a temporary flag to confirm that ClassicPendingScript is not
   // touched after its refinalizer call and thus https://crbug.com/715309
   // doesn't break assumptions.
   // TODO(hiroshige): Check the state in more general way.
   bool prefinalizer_called_ = false;
 };
 
 }  // namespace blink
 
 #endif  // PendingScript_h