Add ContainsKey() and ContainsValue() and use them where appropriate.

core/src/fpdfapi/fpdf_font/ttgsubtable.cpp

Index: core/src/fpdfapi/fpdf_font/ttgsubtable.cpp
diff --git a/core/src/fpdfapi/fpdf_font/ttgsubtable.cpp b/core/src/fpdfapi/fpdf_font/ttgsubtable.cpp
index 035ea8a0ff85f016c083fa107cb3975c4b46ac65..b10aa6952ac03f29490b5faf8dd9f30e72c97a40 100644
--- a/core/src/fpdfapi/fpdf_font/ttgsubtable.cpp
+++ b/core/src/fpdfapi/fpdf_font/ttgsubtable.cpp
@@ -9,6 +9,7 @@
 #include "core/include/fxge/fx_freetype.h"
 #include "core/include/fxge/fx_ge.h"
 #include "third_party/base/nonstd_unique_ptr.h"
+#include "third_party/base/stl_util.h"
 
 CFX_GlyphMap::CFX_GlyphMap() {}
 CFX_GlyphMap::~CFX_GlyphMap() {}
@@ -86,7 +87,7 @@ bool CFX_CTTGSUBTable::GetVerticalGlyph(uint32_t glyphnum,
                 k);
           if (FeatureList.FeatureRecord[index].FeatureTag == tag[0] ||
               FeatureList.FeatureRecord[index].FeatureTag == tag[1]) {
-            if (m_featureMap.find(index) == m_featureMap.end()) {
+            if (!pdfium::ContainsKey(m_featureMap, index)) {
               m_featureMap[index] = index;
             }
           }