Use tighter typing in editing: FormatBlockCommand / FrameSelection

Source/core/editing/InputMethodController.cpp

Index: Source/core/editing/InputMethodController.cpp
diff --git a/Source/core/editing/InputMethodController.cpp b/Source/core/editing/InputMethodController.cpp
index 63bbeb63dd732bce6ca8604f08161d2d3435019a..08778f48daedea147aad0a0ae59d776b1ed01eb3 100644
--- a/Source/core/editing/InputMethodController.cpp
+++ b/Source/core/editing/InputMethodController.cpp
@@ -367,7 +367,7 @@ PlainTextRange InputMethodController::getSelectionOffsets() const
     RefPtrWillBeRawPtr<Range> range = m_frame.selection().selection().firstRange();
     if (!range)
         return PlainTextRange();
-    Node* editable = m_frame.selection().rootEditableElementOrTreeScopeRootNode();
+    ContainerNode* editable = m_frame.selection().rootEditableElementOrTreeScopeRootNode();
     ASSERT(editable);
     return PlainTextRange::create(*editable, *range.get());
 }