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

Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1368 matching lines @@
 VisiblePosition leftBoundaryOfLine(const VisiblePosition& c, TextDirection direction)
 {
     return direction == LTR ? logicalStartOfLine(c) : logicalEndOfLine(c);
 }
 
 VisiblePosition rightBoundaryOfLine(const VisiblePosition& c, TextDirection direction)
 {
     return direction == LTR ? logicalEndOfLine(c) : logicalStartOfLine(c);
 }
 
+LayoutRect localCaretRectOfPosition(const PositionWithAffinity& position, RenderObject*& renderer)
+{
+    if (position.position().isNull()) {
+        renderer = nullptr;
+        return IntRect();
+    }
+    Node* node = position.position().anchorNode();
+
+    renderer = node->renderer();
+    if (!renderer)
+        return LayoutRect();
+
+    InlineBox* inlineBox;
+    int caretOffset;
+    position.position().getInlineBoxAndOffset(position.affinity(), inlineBox, caretOffset);
+
+    if (inlineBox)
+        renderer = &inlineBox->renderer();
+
+    return renderer->localCaretRect(inlineBox, caretOffset);
 }
+
+}