Refactoring ImageProviders

This commit refactors usage of ImageDataProvider and
ImageFilenameProvider to make the code more readable.

contributes to #62 and #127

Author: amartya4256

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

@@ -1167,7 +1167,7 @@ void destroy () {
 
 private void destroyHandle () {
 	for (ImageHandle imageMetadata : zoomLevelToImageHandle.values()) {
-		destroyHandle(imageMetadata);
+		destroyHandle(imageMetadata.handle);
 	}
 	zoomLevelToImageHandle.clear();
 }
@@ -1177,18 +1177,18 @@ void destroyHandlesExcept(Set<Integer> zoomLevels) {
 	zoomLevelToImageHandle.entrySet().removeIf(entry -> {
 		final Integer zoom = entry.getKey();
 		if (!zoomLevels.contains(zoom) && zoom != DPIUtil.getZoomForAutoscaleProperty(initialNativeZoom)) {
-			destroyHandle(entry.getValue());
+			destroyHandle(entry.getValue().handle);
 			return true;
 		}
 		return false;
 	});
 }
 
-private void destroyHandle(ImageHandle imageMetadata) {
+private void destroyHandle(long handle) {
 	if (type == SWT.ICON) {
-		OS.DestroyIcon (imageMetadata.handle);
+		OS.DestroyIcon (handle);
 	} else {
-		OS.DeleteObject (imageMetadata.handle);
+		OS.DeleteObject (handle);
 	}
 }