Add some limit checks to ReadSharedObjHintTable().

core/fpdfapi/fpdf_parser/cpdf_parser.cpp

Index: core/fpdfapi/fpdf_parser/cpdf_parser.cpp
diff --git a/core/fpdfapi/fpdf_parser/cpdf_parser.cpp b/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
index 9d26104caa4c59069293c641d09d69166d83e8db..bd6c8648e0da9da690446fa3d346bdeb55f7b061 100644
--- a/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
+++ b/core/fpdfapi/fpdf_parser/cpdf_parser.cpp
@@ -29,10 +29,6 @@ namespace {
 // this may be large enough in practice.
 const int32_t kMaxXRefSize = 1048576;
 
-// A limit on the maximum object number in the xref table. Theoretical limits
-// are higher, but this may be large enough in practice.
-const uint32_t kMaxObjectNumber = 1048576;
-
 uint32_t GetVarInt(const uint8_t* p, int32_t n) {
   uint32_t result = 0;
   for (int32_t i = 0; i < n; ++i)