Refactor RenderQuote to not delete renderers on style change.

Source/core/rendering/RenderTextFragment.h

Index: Source/core/rendering/RenderTextFragment.h
diff --git a/Source/core/rendering/RenderTextFragment.h b/Source/core/rendering/RenderTextFragment.h
index 55084b1d72cfbf9b5d3ce501cc10b9e360d12bca..505dbabb351a312c9535bdd674d98ae81b6ab662 100644
--- a/Source/core/rendering/RenderTextFragment.h
+++ b/Source/core/rendering/RenderTextFragment.h
@@ -50,7 +50,7 @@ public:
     void setFirstLetter(RenderBoxModelObject* firstLetter) { m_firstLetter = firstLetter; }
     RenderText* firstRenderTextInFirstLetter() const;
 
-    StringImpl* contentString() const { return m_contentString.get(); }
+    void setContentString(StringImpl*);
     virtual PassRefPtr<StringImpl> originalText() const override;
 
     virtual void setText(PassRefPtr<StringImpl>, bool force = false) override;