Get rid of "exceptions" in CBC_QRCoderBitVector::At().

Replace it with a CHECK() that should not fail since all the existing
callers check the bit vector's size.

Change-Id: Id90ca612766661959c7879754dc34ad401402fbd
Reviewed-on: https://pdfium-review.googlesource.com/c/45767
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/fxbarcode/qrcode/BC_QRCoderBitVector.h b/fxbarcode/qrcode/BC_QRCoderBitVector.h
index 0ebeb60..9b8af81 100644
--- a/fxbarcode/qrcode/BC_QRCoderBitVector.h
+++ b/fxbarcode/qrcode/BC_QRCoderBitVector.h
@@ -18,13 +18,13 @@
   ~CBC_QRCoderBitVector();
 
   const uint8_t* GetArray() const;
-  int32_t At(size_t index, int32_t& e) const;
+  int32_t At(size_t index) const;
   size_t Size() const;
   size_t sizeInBytes() const;
 
   void AppendBit(int32_t bit);
   void AppendBits(int32_t value, int32_t numBits);
-  void AppendBitVector(CBC_QRCoderBitVector* bits);
+  void AppendBitVector(const CBC_QRCoderBitVector* bits);
   bool XOR(const CBC_QRCoderBitVector* other);
 
  private: