Use tighter typing in editing: BreakBlockquoteCommand & Caret

Source/core/editing/FrameSelection.h

Index: Source/core/editing/FrameSelection.h
diff --git a/Source/core/editing/FrameSelection.h b/Source/core/editing/FrameSelection.h
index 0cf17a977c43439257da63a0b8287c1d0596ecc7..c949cbd46f956c9c306d778f5e6a59d3dd8d16fc 100644
--- a/Source/core/editing/FrameSelection.h
+++ b/Source/core/editing/FrameSelection.h
@@ -137,7 +137,7 @@ public:
     Position end() const { return m_selection.end(); }
 
     // Return the renderer that is responsible for painting the caret (in the selection start node)
-    RenderObject* caretRenderer() const;
+    RenderBlock* caretRenderer() const;
 
     // Caret rect local to the caret's renderer
     LayoutRect localCaretRect();