Introduce DEFINE_CONTENT_DATA_TYPE_CASTS, and use it

Source/core/rendering/style/ContentData.h

Index: Source/core/rendering/style/ContentData.h
diff --git a/Source/core/rendering/style/ContentData.h b/Source/core/rendering/style/ContentData.h
index 1bf4bf6ef317a6783b6314065af8f5437e81bc70..531091fe06681c8cbbaec8fe1b6bbdfb7ffc913b 100644
--- a/Source/core/rendering/style/ContentData.h
+++ b/Source/core/rendering/style/ContentData.h
@@ -66,6 +66,9 @@ private:
     OwnPtr<ContentData> m_next;
 };
 
+#define DEFINE_CONTENT_DATA_TYPE_CASTS(typeName) \
+    DEFINE_TYPE_CASTS(typeName##ContentData, ContentData, content, content->is##typeName(), content.is##typeName())
+
 class ImageContentData FINAL : public ContentData {
     friend class ContentData;
 public:
@@ -98,6 +101,8 @@ private:
     RefPtr<StyleImage> m_image;
 };
 
+DEFINE_CONTENT_DATA_TYPE_CASTS(Image);
+
 class TextContentData FINAL : public ContentData {
     friend class ContentData;
 public:
@@ -125,6 +130,8 @@ private:
     String m_text;
 };
 
+DEFINE_CONTENT_DATA_TYPE_CASTS(Text);
+
 class CounterContentData FINAL : public ContentData {
     friend class ContentData;
 public:
@@ -156,6 +163,8 @@ private:
     OwnPtr<CounterContent> m_counter;
 };
 
+DEFINE_CONTENT_DATA_TYPE_CASTS(Counter);
+
 class QuoteContentData FINAL : public ContentData {
     friend class ContentData;
 public:
@@ -183,6 +192,8 @@ private:
     QuoteType m_quote;
 };
 
+DEFINE_CONTENT_DATA_TYPE_CASTS(Quote);
+
 inline bool operator==(const ContentData& a, const ContentData& b)
 {
     return a.equals(b);