[win32] do not call getImageData on getBounds call

This commit unifies the getBounds calculation for ImageDataProvider and
ImageFileNameProvider by always scaling the bounds of an existing handle
of an image, if the bounds for a different zoom are requested.

fixes #1639

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Image.java

@@ -2185,9 +2185,9 @@ private class ImageDataProviderWrapper extends AbstractImageProviderWrapper {
 
 	@Override
 	protected Rectangle getBounds(int zoom) {
-		ElementAtZoom<ImageData> data = DPIUtil.validateAndGetImageDataAtZoom (provider, zoom);
-		Rectangle rectangle = new Rectangle(0, 0, data.element().width, data.element().height);
-		return DPIUtil.scaleBounds(rectangle, zoom, data.zoom());
+		ImageHandle imageHandle = zoomLevelToImageHandle.values().iterator().next();
+		Rectangle rectangle = new Rectangle(0, 0, imageHandle.width, imageHandle.height);
+		return DPIUtil.scaleBounds(rectangle, zoom, imageHandle.zoom);
 	}
 
 	@Override