Create bitmaps even when given a wxDC without an HDC in wxMSW

It seems wrong to just fail to create the bitmap entirely if a not
wxMSWDCImpl-derived wxDC is provided to wxBitmap::Create(size, wxDC)
overload, especially because no check is done to see if the associated
HDC is non-null for wxMSWDCImpl-derived classes.

Instead, simply create a DIB-based bitmap with the specified size, as
this seems more useful and less surprising and was already the behaviour
in the other ports.

Add a test ensuring that this remains the case in the future.

src/msw/bitmap.cpp

@@ -755,12 +755,7 @@ bool wxBitmap::Create(int width, int height, const wxDC& dc)
 {
     wxCHECK_MSG( dc.IsOk(), false, wxT("invalid HDC in wxBitmap::Create()") );
 
-    const wxMSWDCImpl *impl = wxDynamicCast( dc.GetImpl(), wxMSWDCImpl );
-
-    if (impl)
-        return DoCreate(width, height, -1, impl->GetHDC());
-    else
-        return false;
+    return DoCreate(width, height, -1, dc.GetHDC());
 }
 
 bool wxBitmap::CreateWithDIPSize(const wxSize& size, double scale, int depth)

tests/graphics/bitmap.cpp

@@ -18,6 +18,7 @@
 #include "wx/bitmap.h"
 #include "wx/rawbmp.h"
 #include "wx/dcmemory.h"
+#include "wx/dcsvg.h"
 #if wxUSE_GRAPHICS_CONTEXT
 #include "wx/graphics.h"
 #endif // wxUSE_GRAPHICS_CONTEXT
@@ -1690,6 +1691,16 @@ TEST_CASE("DC::Clear", "[bitmap][dc]")
     }
 }
 
+TEST_CASE("Bitmap::DC", "[bitmap][dc]")
+{
+#if wxUSE_SVG
+    TempFile dummySVG("dummy.svg");
+    wxSVGFileDC dc(dummySVG.GetName());
+    wxBitmap bmp(10, 10, dc);
+    CHECK( bmp.IsOk() );
+#endif // wxUSE_SVG
+}
+
 #if wxUSE_GRAPHICS_CONTEXT
 
 inline void DrawScaledBmp(wxBitmap& bmp, float scale, wxGraphicsRenderer* renderer)