Autotest: extract cpp document lookup into cpp test parser

Change-Id: I261684206ec7ff9a97ca4a88b5846ebbc0fdda47
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/autotest/itestparser.cpp

@@ -78,5 +78,10 @@ void CppParser::release()
     m_workingCopy = CppTools::WorkingCopy();
 }
 
+CPlusPlus::Document::Ptr CppParser::document(const QString &fileName)
+{
+    return selectedForBuilding(fileName) ? m_cppSnapshot.document(fileName) : nullptr;
+}
+
 } // namespace Internal
 } // namespace Autotest