De-duplicate definition of struct PixelWeight

The identical struct exists at top-level in fx_dib.h, as well as a
nested definition in ProgressiveDecoder. Keep the top-level one as
it is used in several places.

Change-Id: Ia83f0bf66730f3a4818b4d35ef09cfb47f29ec7a
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/75670
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxcodec/progressive_decoder.h b/core/fxcodec/progressive_decoder.h
index 9244df8..561660a 100644
--- a/core/fxcodec/progressive_decoder.h
+++ b/core/fxcodec/progressive_decoder.h
@@ -88,12 +88,6 @@
 
   FXCODEC_STATUS ContinueDecode();
 
-  struct PixelWeight {
-    int m_SrcStart;
-    int m_SrcEnd;
-    int m_Weights[1];
-  };
-
   class CFXCODEC_WeightTable {
    public:
     CFXCODEC_WeightTable();