Add function to access QLockFile's file name

This is useful in cases like error handling when you need to print the
name of the lock file.

Change-Id: Ife4901ed53ae81d19e68cce7f1c173ef3745d56f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qlockfile.cpp

@@ -150,6 +150,14 @@ QLockFile::~QLockFile()
     unlock();
 }
 
+/*!
+ * Returns the file name of the lock file
+ */
+QString QLockFile::fileName() const
+{
+    return d_ptr->fileName;
+}
+
 /*!
     Sets \a staleLockTime to be the time in milliseconds after which
     a lock file is considered stale.

src/corelib/io/qlockfile.h

@@ -53,6 +53,8 @@ public:
     QLockFile(const QString &fileName);
     ~QLockFile();
 
+    QString fileName() const;
+
     bool lock();
     bool tryLock(int timeout = 0);
     void unlock();

tests/auto/corelib/io/qlockfile/tst_qlockfile.cpp

@@ -96,6 +96,7 @@ void tst_QLockFile::lockUnlock()
     const QString fileName = dir.path() + "/lock1";
     QVERIFY(!QFile(fileName).exists());
     QLockFile lockFile(fileName);
+    QCOMPARE(lockFile.fileName(), fileName);
     QVERIFY(lockFile.lock());
     QVERIFY(lockFile.isLocked());
     QCOMPARE(int(lockFile.error()), int(QLockFile::NoError));