Move ByteStringPool from document to indirect object holder.

core/fpdfapi/parser/cpdf_indirect_object_holder.cpp

Index: core/fpdfapi/parser/cpdf_indirect_object_holder.cpp
diff --git a/core/fpdfapi/parser/cpdf_indirect_object_holder.cpp b/core/fpdfapi/parser/cpdf_indirect_object_holder.cpp
index 12b1e9f0896fc8c1d969b094c3a045707f85a29b..d1183ebaf470e3ee6a7deab98d38bf1646156baf 100644
--- a/core/fpdfapi/parser/cpdf_indirect_object_holder.cpp
+++ b/core/fpdfapi/parser/cpdf_indirect_object_holder.cpp
@@ -9,9 +9,13 @@
 #include "core/fpdfapi/parser/cpdf_object.h"
 #include "core/fpdfapi/parser/cpdf_parser.h"
 
-CPDF_IndirectObjectHolder::CPDF_IndirectObjectHolder() : m_LastObjNum(0) {}
+CPDF_IndirectObjectHolder::CPDF_IndirectObjectHolder()
+    : m_LastObjNum(0),
+      m_pByteStringPool(pdfium::MakeUnique<CFX_ByteStringPool>()) {}
 
-CPDF_IndirectObjectHolder::~CPDF_IndirectObjectHolder() {}
+CPDF_IndirectObjectHolder::~CPDF_IndirectObjectHolder() {
+  m_pByteStringPool.DeleteObject();  // Make weak.
+}
 
 CPDF_Object* CPDF_IndirectObjectHolder::GetIndirectObject(
     uint32_t objnum) const {