Add a separate call to initialize the bounds for a sky <iframe> element.

sky/engine/core/html/HTMLIFrameElement.h

Index: sky/engine/core/html/HTMLIFrameElement.h
diff --git a/sky/engine/core/html/HTMLIFrameElement.h b/sky/engine/core/html/HTMLIFrameElement.h
index 577f4b1d47699a15791ab825be01850f26b38544..f1c10ce7386f4e7a0c10177ddac7cc92fa024521 100644
--- a/sky/engine/core/html/HTMLIFrameElement.h
+++ b/sky/engine/core/html/HTMLIFrameElement.h
@@ -19,6 +19,8 @@ public:
 
     virtual ~HTMLIFrameElement();
 
+    uint32_t frame_id() const { return frame_id_; }
+
 private:
     explicit HTMLIFrameElement(Document&);
 
@@ -29,6 +31,8 @@ private:
 
 private:
     void createView();
+
+    uint32_t frame_id_;
 };
 
 } // namespace blink