Show a warning when using sync xhr.

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index dc9f9faa7a925e9274be4954385f38444b20b0ed..946542f0aebc142288d069f24342245c54b9b8c6 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -1041,6 +1041,9 @@ public:
     virtual v8::Handle<v8::Object> wrap(v8::Handle<v8::Object> creationContext, v8::Isolate*) OVERRIDE;
     virtual v8::Handle<v8::Object> associateWithWrapper(const WrapperTypeInfo*, v8::Handle<v8::Object> wrapper, v8::Isolate*) OVERRIDE;
 
+    void setWarnedAboutSyncXHROnce() { m_warnAboutSyncXHROnce = true; }
+    bool didWarnAboutSyncXHROnce() { return m_warnAboutSyncXHROnce; }
+
 protected:
     Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
@@ -1372,6 +1375,7 @@ private:
     DocumentVisibilityObserverSet m_visibilityObservers;
 
     int m_styleRecalcElementCounter;
+    bool m_warnAboutSyncXHROnce;

[kouhei (in TOK), 2014/10/01 11:38:44]

m_hasWarnedAboutSyncXHR?

I want to avoid adding the flag in Document as much as possible, but I don't
have a suggestion of alternative now...

 };
 
 inline bool Document::shouldOverrideLegacyDescription(ViewportDescription::Type origin)