Fix -Wunused-function warnings on Windows.

BUG=505316
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1293033002 .
diff --git a/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp b/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
index 6c72824..5927511 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
@@ -832,6 +832,8 @@
 FX_BOOL CPDF_CIDFont::IsVertWriting() const {
   return m_pCMap ? m_pCMap->IsVertWriting() : FALSE;
 }
+
+#if _FXM_PLATFORM_ != _FXM_PLATFORM_WINDOWS_
 extern FX_DWORD FPDFAPI_CharCodeFromCID(const FXCMAP_CMap* pMap, FX_WORD cid);
 static FX_DWORD _EmbeddedCharcodeFromUnicode(const FXCMAP_CMap* pEmbedMap,
                                              int charset,
@@ -857,6 +859,8 @@
   }
   return 0;
 }
+#endif  // _FXM_PLATFORM_ != _FXM_PLATFORM_WINDOWS_
+
 static FX_WCHAR _EmbeddedUnicodeFromCharcode(const FXCMAP_CMap* pEmbedMap,
                                              int charset,
                                              FX_DWORD charcode) {
diff --git a/core/src/fxge/win32/fx_win32_gdipext.cpp b/core/src/fxge/win32/fx_win32_gdipext.cpp
index ce65a26..4beef9a 100644
--- a/core/src/fxge/win32/fx_win32_gdipext.cpp
+++ b/core/src/fxge/win32/fx_win32_gdipext.cpp
@@ -5,27 +5,26 @@
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../../include/fxge/fx_ge.h"
+
 #if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN64_DESKTOP_
 #include <windows.h>
 #include <algorithm>
+
 namespace Gdiplus {
 using std::min;
 using std::max;
 }  // namespace Gdiplus
+
 #include <gdiplus.h>
 #include "../../../include/fxge/fx_ge_win32.h"
 #include "win32_int.h"
+
 using namespace Gdiplus;
 using namespace Gdiplus::DllExports;
+
 #define GdiFillType2Gdip(fill_type) \
   (fill_type == ALTERNATE ? FillModeAlternate : FillModeWinding)
-static CombineMode GdiCombineMode2Gdip(int mode) {
-  switch (mode) {
-    case RGN_AND:
-      return CombineModeIntersect;
-  }
-  return CombineModeIntersect;
-}
+
 enum {
   FuncId_GdipCreatePath2,
   FuncId_GdipSetPenDashStyle,