Make several CJBig2_Image methods private

They have no external callers.

Change-Id: I509ee440b2285df51adf857cdd753fae75ae1ff1
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/147711
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fxcodec/jbig2/jbig2_image.h

diff --git a/core/fxcodec/jbig2/jbig2_image.h b/core/fxcodec/jbig2/jbig2_image.h
index 69935a5..712eac0 100644
--- a/core/fxcodec/jbig2/jbig2_image.h
+++ b/core/fxcodec/jbig2/jbig2_image.h
@@ -60,8 +60,6 @@
   // Returns an empty span if `y` is out of bounds, or if there is no data.
   pdfium::span<const uint8_t> GetLine(int32_t y) const;
   pdfium::span<uint8_t> GetLine(int32_t y);
-  pdfium::span<const uint32_t> GetLine32(int32_t y) const;
-  pdfium::span<uint32_t> GetLine32(int32_t y);
 
   void CopyLine(pdfium::span<uint8_t> dest, pdfium::span<const uint8_t> src);
   void Fill(bool v);
@@ -80,15 +78,19 @@
   void Expand(int32_t h, bool v);
 
   bool ComposeTo(CJBig2_Image* pDst, int64_t x, int64_t y, JBig2ComposeOp op);
+
+ private:
+  std::optional<size_t> GetLineOffset(int32_t y) const;
+
+  pdfium::span<const uint32_t> GetLine32(int32_t y) const;
+  pdfium::span<uint32_t> GetLine32(int32_t y);
+
   bool ComposeToWithRect(CJBig2_Image* pDst,
                          int64_t x,
                          int64_t y,
                          const FX_RECT& rtSrc,
                          JBig2ComposeOp op);
 
- private:
-  std::optional<size_t> GetLineOffset(int32_t y) const;
-
   // SubImage() already checked `x` and `y` are valid.
   void SubImageFast(uint32_t x,
                     uint32_t y,