Merge Blink code to cache SkTextBlob

sky/engine/core/rendering/InlineTextBox.h

Index: sky/engine/core/rendering/InlineTextBox.h
diff --git a/sky/engine/core/rendering/InlineTextBox.h b/sky/engine/core/rendering/InlineTextBox.h
index ab67eeee904ae9dc87d21f5dbf035165ba20f430..76696f918d8509aea524ad18ff207ec26adca182 100644
--- a/sky/engine/core/rendering/InlineTextBox.h
+++ b/sky/engine/core/rendering/InlineTextBox.h
@@ -161,6 +161,7 @@ public:
 private:
     InlineTextBox* m_prevTextBox; // The previous box that also uses our RenderObject
     InlineTextBox* m_nextTextBox; // The next box that also uses our RenderObject
+    TextBlobPtr m_cachedTextBlob;
 
     int m_start;
     unsigned short m_len;