Show a warning when using sync xhr.

Source/core/dom/ExecutionContext.h

Index: Source/core/dom/ExecutionContext.h
diff --git a/Source/core/dom/ExecutionContext.h b/Source/core/dom/ExecutionContext.h
index 840698044bb057c3e1e084d9412daca69cffd064..4e483bed9be53c50c18565dbc899e82b5e2e3899 100644
--- a/Source/core/dom/ExecutionContext.h
+++ b/Source/core/dom/ExecutionContext.h
@@ -130,6 +130,8 @@ public:
 
     virtual EventTarget* errorEventTarget() = 0;
     virtual EventQueue* eventQueue() const = 0;
+    virtual bool inBeforeUnloadEvent() const { return m_inBeforeUnloadEvent; }
+    virtual void setIsBeforeUnloadEvent(bool inBeforeUnloadEvent) { m_inBeforeUnloadEvent = inBeforeUnloadEvent; }

[kouhei (in TOK), 2014/10/01 11:38:45]

Can you use lifecycle methods in Document instead?

https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

 
 protected:
     ExecutionContext();
@@ -174,6 +176,7 @@ private:
     // ExecutionContext's members (notably m_timeouts) is called before they are destructed,
     // m_lifecycleNotifer should be placed *after* such members.
     OwnPtr<ContextLifecycleNotifier> m_lifecycleNotifier;
+    bool m_inBeforeUnloadEvent;
 };
 
 } // namespace blink