Let FrameSelection::localCaretRect on a text input field avoid synchronous layout.

Source/core/editing/Caret.h

Index: Source/core/editing/Caret.h
diff --git a/Source/core/editing/Caret.h b/Source/core/editing/Caret.h
index 34febde4c89cd0703561c6358c5baa17fb418003..728f36e852e7cc07caa0ee9adfdaa5f4687d692c 100644
--- a/Source/core/editing/Caret.h
+++ b/Source/core/editing/Caret.h
@@ -35,6 +35,7 @@ namespace blink {
 
 class LocalFrame;
 class GraphicsContext;
+class PositionWithAffinity;
 class RenderBlock;
 class RenderView;
 
@@ -47,6 +48,8 @@ protected:
 
     void invalidateCaretRect(Node*, bool caretRectChanged = false);
     void clearCaretRect();
+    bool updateCaretRect(Document*, const PositionWithAffinity& caretPosition);
+    // Simply calls above updateCaretRect using deepEquivalent() and affinity().

[tkent, 2014/07/30 00:29:33]

This comment is not helpful.
Please write a comment to help a developer who wants to call updateCaretRect.
The important difference is synchronous layout, and we should use the former
version if possible, right?

     bool updateCaretRect(Document*, const VisiblePosition& caretPosition);
     IntRect absoluteBoundsForLocalRect(Node*, const LayoutRect&) const;
     bool shouldRepaintCaret(const RenderView*, bool isContentEditable) const;