Introduce rootEditableElementOrTreeScopeRootNodeOf() as replacement of FrameSelection member

third_party/WebKit/Source/core/editing/InputMethodController.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 680 matching lines @@
   return plainText(
       compositionEphemeralRange(),
       TextIteratorBehavior::Builder().setEmitsOriginalText(true).build());
 }
 
 PlainTextRange InputMethodController::getSelectionOffsets() const {
   EphemeralRange range = firstEphemeralRangeOf(
       frame().selection().computeVisibleSelectionInDOMTreeDeprecated());
   if (range.isNull())
     return PlainTextRange();
-  ContainerNode* editable =
-      frame().selection().rootEditableElementOrTreeScopeRootNode();
+  ContainerNode* const editable = rootEditableElementOrTreeScopeRootNodeOf(
+      frame().selection().computeVisibleSelectionInDOMTreeDeprecated());
   DCHECK(editable);
   return PlainTextRange::create(*editable, range);
 }
 
 EphemeralRange InputMethodController::ephemeralRangeForOffsets(
     const PlainTextRange& offsets) const {
   if (offsets.isNull())
     return EphemeralRange();
   Element* rootEditableElement =
       frame()
@@ skipping 412 matching lines @@
   finishComposingText(KeepSelection);
 }
 
 DEFINE_TRACE(InputMethodController) {
   visitor->trace(m_frame);
   visitor->trace(m_compositionRange);
   SynchronousMutationObserver::trace(visitor);
 }
 
 }  // namespace blink