Disallow more CFX_ScanlineCompositor conversions.

Disallow the combination where the destination bitmap format uses
palettes and the reverse byte order bit is set. CFX_ScanlineCompositor
is not designed to handle this case, and will end up doing the wrong
thing. e.g. for a source format of `FXDIB_Argb` and destination format
of `FXDIB_8bppRgba`, it will call
CompositeRow_Rgb2Argb_NoBlend_NoClip_RgbByteOrder(), which is
completely nonsensical.

Bug: chromium:1139825
Change-Id: I6a4d7a402d4006d7454188cf9f66daa04ed98062
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/75470
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxge/dib/cfx_scanlinecompositor.cpp b/core/fxge/dib/cfx_scanlinecompositor.cpp
index 5e25641..ab62044 100644
--- a/core/fxge/dib/cfx_scanlinecompositor.cpp
+++ b/core/fxge/dib/cfx_scanlinecompositor.cpp
@@ -2753,7 +2753,7 @@
   if (GetBppFromFormat(dest_format) == 1)
     return false;
-  if (m_bRgbByteOrder && m_DestFormat == FXDIB_Format::k8bppMask)
+  if (m_bRgbByteOrder && GetBppFromFormat(m_DestFormat) == 8)
     return false;
   if (m_SrcFormat == FXDIB_Format::k1bppMask ||