CppTools: Add sourceFilePath to AbstractEditorSupport

Provide the source path to track a generated file source. You can for
example get the modified time stamp for the source file and use it for the
generated file content.

Task-number: QTCREATORBUG-21876
Change-Id: Ia422e128c5cb7a3dce88960f126152c2f65afb41
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cpptools/generatedcodemodelsupport.cpp

@@ -108,6 +108,11 @@ QString GeneratedCodeModelSupport::fileName() const
     return m_generatedFileName.toString();
 }
 
+QString GeneratedCodeModelSupport::sourceFileName() const
+{
+    return m_generator->source().toString();
+}
+
 void GeneratedCodeModelSupport::update(const QList<ProjectExplorer::ExtraCompiler *> &generators)
 {
     static QObjectCache extraCompilerCache;