Use current selection when tab navigation.

third_party/WebKit/Source/core/editing/FrameSelection.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 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
@@ skipping 212 matching lines @@
 
   void SetFocusedNodeIfNeeded();
   void NotifyTextControlOfSelectionChange(EUserTriggered);
 
   String SelectedHTMLForClipboard() const;
   String SelectedText(const TextIteratorBehavior&) const;
   String SelectedText() const;
   String SelectedTextForClipboard() const;
 
   // The bounds are clipped to the viewport as this is what callers expect.
+  // This returns last layouted selection bounds of LayoutSelection rather than
+  // SelectionEditor keeps.
   LayoutRect Bounds() const;
   LayoutRect UnclippedBounds() const;
 
   // TODO(tkent): This function has a bug that scrolling doesn't work well in
   // a case of RangeSelection. crbug.com/443061
   void RevealSelection(
       const ScrollAlignment& = ScrollAlignment::kAlignCenterIfNeeded,
       RevealExtentOption = kDoNotRevealExtent);
   void SetSelectionFromNone();
 
@@ skipping 67 matching lines @@
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::FrameSelection&);
 void showTree(const blink::FrameSelection*);
 #endif
 
 #endif  // FrameSelection_h