CodeAssist: Use settable property for IAssistProposal::isFragile

Removes the need to create yet another subclass (for overriding a
virtual method) in some situations.

Change-Id: I55d70de60b4f8d127a175d996f797700c2f172a6
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/texteditor/codeassist/iassistproposal.cpp

@@ -85,6 +85,11 @@ int IAssistProposal::basePosition() const
     return m_basePosition;
 }
 
+bool IAssistProposal::isFragile() const
+{
+    return m_isFragile;
+}
+
 /*!
     \fn bool TextEditor::IAssistProposal::isCorrective() const
 
@@ -110,6 +115,11 @@ void IAssistProposal::makeCorrection(TextEditorWidget *editorWidget)
     Q_UNUSED(editorWidget);
 }
 
+void IAssistProposal::setFragile(bool fragile)
+{
+    m_isFragile = fragile;
+}
+
 /*!
     \fn IAssistModel *TextEditor::IAssistProposal::model() const