Add test for CPDF_StreamParser::ReadHexString.

core/src/fpdfapi/fpdf_page/pageint.h

Index: core/src/fpdfapi/fpdf_page/pageint.h
diff --git a/core/src/fpdfapi/fpdf_page/pageint.h b/core/src/fpdfapi/fpdf_page/pageint.h
index 1b41633346d2db849ffb98672887560f6eb3d7cf..e787d6973a4f36edb3e45fab5fd9fa630c56a698 100644
--- a/core/src/fpdfapi/fpdf_page/pageint.h
+++ b/core/src/fpdfapi/fpdf_page/pageint.h
@@ -10,8 +10,12 @@
 #include <map>
 
 #include "../../../../third_party/base/nonstd_unique_ptr.h"
+#include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_pageobj.h"
 
+class CPDF_AllStates;
+class CPDF_ParseOptions;
+
 #define PARSE_STEP_LIMIT 100
 
 class CPDF_StreamParser {
@@ -41,6 +45,8 @@ class CPDF_StreamParser {
   void SkipPathObject();
 
  protected:
+  friend class fpdf_page_parser_old_ReadHexString_Test;
+
   void GetNextWord(FX_BOOL& bIsNumber);
   CFX_ByteString ReadString();
   CFX_ByteString ReadHexString();