Use std::map as CPDF_Dictionary's underlying store.

core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp

Index: core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
diff --git a/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp b/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
index d8f21c692de4b316a7c5fa071a8abf305b1c06ff..dd16aa85ce6d387ab75868c4de6de1ecc3b2b5cd 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_graph_state.cpp
@@ -458,10 +458,9 @@ void CPDF_AllStates::SetLineDash(CPDF_Array* pArray,
 void CPDF_AllStates::ProcessExtGS(CPDF_Dictionary* pGS,
                                   CPDF_StreamContentParser* pParser) {
   CPDF_GeneralStateData* pGeneralState = m_GeneralState.GetModify();
-  FX_POSITION pos = pGS->GetStartPos();
-  while (pos) {
-    CFX_ByteString key_str;
-    CPDF_Object* pElement = pGS->GetNextElement(pos, key_str);
+  for (const auto& it : *pGS) {
+    const CFX_ByteString& key_str = it.first;
+    CPDF_Object* pElement = it.second;
     CPDF_Object* pObject = pElement ? pElement->GetDirect() : nullptr;
     if (!pObject)
       continue;