Convert some call sites to use explicit LayoutRect->FloatRect conversion.

Source/core/editing/Editor.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
@@ skipping 1068 matching lines @@
     if (selectionDidNotChangeDOMPosition)
         client().respondToChangedSelection(m_frame, frame().selection().selectionType());
 }
 
 IntRect Editor::firstRectForRange(const EphemeralRange& range) const
 {
     LayoutUnit extraWidthToEndOfLine = 0;
     ASSERT(range.isNotNull());
 
     IntRect startCaretRect = RenderedPosition(VisiblePosition(range.startPosition()).deepEquivalent(), TextAffinity::Downstream).absoluteRect(&extraWidthToEndOfLine);
-    if (startCaretRect == LayoutRect())
+    if (startCaretRect.isEmpty())
         return IntRect();
 
     IntRect endCaretRect = RenderedPosition(VisiblePosition(range.endPosition()).deepEquivalent(), TextAffinity::Upstream).absoluteRect();
-    if (endCaretRect == LayoutRect())
+    if (endCaretRect.isEmpty())
         return IntRect();
 
     if (startCaretRect.y() == endCaretRect.y()) {
         // start and end are on the same line
         return IntRect(std::min(startCaretRect.x(), endCaretRect.x()),
             startCaretRect.y(),
             abs(endCaretRect.x() - startCaretRect.x()),
             std::max(startCaretRect.height(), endCaretRect.height()));
     }
 
@@ skipping 197 matching lines @@
 }
 
 DEFINE_TRACE(Editor)
 {
     visitor->trace(m_frame);
     visitor->trace(m_lastEditCommand);
     visitor->trace(m_mark);
 }
 
 } // namespace blink