Scale requestGrabWindow()'s image to fit size of window grab

grabbedFrame.image is sized according to display scaling, but
the contents of the image itself remain at their original,
non-scaled, resolution. There's a slim chance that the image is
scaled to fit the scaled canvas, and the quickinspectortest
passes. Most of the times, however, the image won't be scaled
to fit the canvas.

In this change we manually scale the image according to
devicePixelRatio to fit the image's canvas. This allows the test
to pass while keeping it unmodified.

plugins/quickinspector/quickscreengrabber.cpp

@@ -806,8 +806,14 @@ UnsupportedScreenGrabber::~UnsupportedScreenGrabber()
 
 void UnsupportedScreenGrabber::requestGrabWindow(const QRectF & /*userViewport*/)
 {
+    const qreal ratio = m_window->effectiveDevicePixelRatio();
+    const int width = m_window->width(),
+              height = m_window->height();
     m_grabbedFrame.image = m_window->grabWindow();
-    m_grabbedFrame.image.setDevicePixelRatio(m_window->effectiveDevicePixelRatio());
+    if (ratio == 1.0)
+        m_grabbedFrame.image = m_grabbedFrame.image.copy(0, 0, width, height);
+    else
+        m_grabbedFrame.image = m_grabbedFrame.image.copy(0, 0, width, height).scaledToHeight(height * ratio);
 
     int alpha = 120;
     if (m_grabbedFrame.image.isNull()) {