QWin32PrintEngine: Fix uninitialized memory read of dpi_x, dpi_y

Discovered by purify:
QWin32PrintEnginePrivate::initialize() called updateMetrics()
via updatePageLayout() after initHDC(), so dpi_x, dpi_y
were accessed before initialized from the display resolution.
Fix by moving the call initHDC() up and giving default
values.

Change-Id: Ia360c06d156e569ca6b1472ec5b5cdc52948f913
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

src/printsupport/kernel/qprintengine_win.cpp

@@ -918,14 +918,14 @@ void QWin32PrintEnginePrivate::initialize()
     Q_ASSERT(hPrinter);
     Q_ASSERT(pInfo);
 
+    initHDC();
+
     if (devMode) {
         num_copies = devMode->dmCopies;
         devMode->dmCollate = DMCOLLATE_TRUE;
         updatePageLayout();
     }
 
-    initHDC();
-
 #if defined QT_DEBUG_DRAW || defined QT_DEBUG_METRICS
     qDebug() << "QWin32PrintEngine::initialize()";
     debugMetrics();

src/printsupport/kernel/qprintengine_win_p.h

@@ -124,10 +124,14 @@ public:
         state(QPrinter::Idle),
         resolution(0),
         m_pageLayout(QPageLayout(QPageSize(QPageSize::A4), QPageLayout::Portrait, QMarginsF(0, 0, 0, 0))),
+        stretch_x(1), stretch_y(1), origin_x(0), origin_y(0),
+        dpi_x(96), dpi_y(96), dpi_display(96),
         num_copies(1),
         printToFile(false),
         reinit(false),
-        embed_fonts(true)
+        complex_xform(false), has_pen(false), has_brush(false), has_custom_paper_size(false),
+        embed_fonts(true),
+        txop(0 /* QTransform::TxNone */)
     {
     }