Introduce a lifecycle model to WindowProxy

third_party/WebKit/Source/bindings/core/v8/WindowProxy.h

Index: third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h b/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
index 7373e0f62f9774c9e338cf43d83d7ae01ddb5092..54cf8b4a7be14fd66873f80820549809c99c921c 100644
--- a/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
+++ b/third_party/WebKit/Source/bindings/core/v8/WindowProxy.h
@@ -52,6 +52,14 @@ class SecurityOrigin;
 // persist between navigations.
 class WindowProxy final : public GarbageCollectedFinalized<WindowProxy> {
  public:
+  // A valid transition is from ContextUninitialized to ContextInitialized,
+  // and then ContextDetached. Other transitions are forbidden.
+  enum class Lifecycle {

[Yuki, 2017/01/06 12:56:56]

nit: We can move this into private: section?

+    ContextUninitialized,
+    ContextInitialized,
+    ContextDetached,
+  };
+
   static WindowProxy* create(v8::Isolate*, Frame*, DOMWrapperWorld&);
 
   ~WindowProxy();
@@ -72,9 +80,6 @@ class WindowProxy final : public GarbageCollectedFinalized<WindowProxy> {
   // (e.g., after setting docoument.domain).
   void updateSecurityOrigin(SecurityOrigin*);
 
-  bool isContextInitialized() {
-    return m_scriptState && !!m_scriptState->perContextData();
-  }
   void initializeIfNeeded();
 
   void clearForNavigation();
@@ -118,6 +123,7 @@ class WindowProxy final : public GarbageCollectedFinalized<WindowProxy> {
   RefPtr<ScriptState> m_scriptState;
   RefPtr<DOMWrapperWorld> m_world;
   ScopedPersistent<v8::Object> m_globalProxy;
+  Lifecycle m_lifecycle;
 };
 
 }  // namespace blink