Core: Avoid copy in IDocument::filePath()

Change-Id: I40d5ebc73856e85e36080b94e071edef15242666
Reviewed-by: Daniel Teske <daniel.teske@theqtcompany.com>

src/plugins/coreplugin/idocument.cpp

@@ -129,7 +129,7 @@ bool IDocument::setContents(const QByteArray &contents)
     return false;
 }
 
-Utils::FileName IDocument::filePath() const
+const Utils::FileName &IDocument::filePath() const
 {
     return d->filePath;
 }

src/plugins/coreplugin/idocument.h

@@ -89,7 +89,7 @@ public:
     virtual bool save(QString *errorString, const QString &fileName = QString(), bool autoSave = false) = 0;
     virtual bool setContents(const QByteArray &contents);
 
-    Utils::FileName filePath() const;
+    const Utils::FileName &filePath() const;
     virtual void setFilePath(const Utils::FileName &filePath);
     QString displayName() const;
     void setPreferredDisplayName(const QString &name);