Introduce rootEditableElementOrTreeScopeRootNodeOf() as replacement of FrameSelection member

third_party/WebKit/Source/core/editing/commands/TypingCommand.cpp

Index: third_party/WebKit/Source/core/editing/commands/TypingCommand.cpp
diff --git a/third_party/WebKit/Source/core/editing/commands/TypingCommand.cpp b/third_party/WebKit/Source/core/editing/commands/TypingCommand.cpp
index 7313874cb3719a3740746c01431fd621de89ba60..e47b8b27d0ba607435d0a760bdd461d957cb98f9 100644
--- a/third_party/WebKit/Source/core/editing/commands/TypingCommand.cpp
+++ b/third_party/WebKit/Source/core/editing/commands/TypingCommand.cpp
@@ -85,8 +85,8 @@ PlainTextRange getSelectionOffsets(LocalFrame* frame) {
       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);
 }