Update DirectWrite code so that it is loadable on XP.

src/ports/SkFontHost_win_dw.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTypes.h"
 #undef GetGlyphIndices
 
@@ skipping 79 matching lines @@
 
 private:
     uint16_t fWidth;
     uint16_t fHeight;
     IDWriteFontFace* fFontFace;
     FLOAT fFontSize;
     DWRITE_MATRIX fXform;
     SkTDArray<uint8_t> fBits;
 };
 
-typedef HRESULT (WINAPI *DWriteCreateFactoryProc)(
-    __in DWRITE_FACTORY_TYPE factoryType,
-    __in REFIID iid,
-    __out IUnknown **factory
-);
-
 static HRESULT get_dwrite_factory(IDWriteFactory** factory) {
     static IDWriteFactory* gDWriteFactory = NULL;
 
     if (gDWriteFactory != NULL) {
         *factory = gDWriteFactory;
         return S_OK;
     }
 
+    typedef decltype(DWriteCreateFactory)* DWriteCreateFactoryProc;
     DWriteCreateFactoryProc dWriteCreateFactoryProc =
         reinterpret_cast<DWriteCreateFactoryProc>(
             GetProcAddress(LoadLibraryW(L"dwrite.dll"), "DWriteCreateFactory")
         )
     ;
 
     if (!dWriteCreateFactoryProc) {
         return E_UNEXPECTED;
     }
 
@@ skipping 1716 matching lines @@
     printf("SkFontHost::CreateTypefaceFromFile unimplemented");
     return NULL;
 }
 
 SkTypeface* SkFontHost::CreateTypefaceFromStream(SkStream* stream) {
     return create_from_stream(stream, 0);
 }
 
 #endif
 
+typedef decltype(GetUserDefaultLocaleName)* GetUserDefaultLocaleNameProc;
+static GetUserDefaultLocaleNameProc GetGetUserDefaultLocaleNameProc() {
+    return reinterpret_cast<GetUserDefaultLocaleNameProc>(
+        GetProcAddress(LoadLibraryW(L"Kernel32.dll"), "GetUserDefaultLocaleName")
+    );
+}
+
 SkFontMgr* SkFontMgr::Factory() {
     IDWriteFactory* factory;
     HRNM(get_dwrite_factory(&factory), "Could not get factory.");
 
     SkTScopedComPtr<IDWriteFontCollection> sysFontCollection;
     HRNM(factory->GetSystemFontCollection(&sysFontCollection, FALSE),
          "Could not get system font collection.");
 
     WCHAR localeNameStorage[LOCALE_NAME_MAX_LENGTH];
     WCHAR* localeName = NULL;
-    int localeNameLen = GetUserDefaultLocaleName(localeNameStorage, LOCALE_NAME_MAX_LENGTH);
-    if (localeNameLen) {
-        localeName = localeNameStorage;
-    };
+    int localeNameLen = 0;
+
+    // Dynamically load GetUserDefaultLocaleName function, as it is not available on XP.
+    GetUserDefaultLocaleNameProc getUserDefaultLocaleNameProc = GetGetUserDefaultLocaleNameProc();
+    if (NULL == getUserDefaultLocaleNameProc) {
+        SkDebugf("Could not get GetUserDefaultLocaleName.");
+    } else {
+        localeNameLen = getUserDefaultLocaleNameProc(localeNameStorage, LOCALE_NAME_MAX_LENGTH);
+        if (localeNameLen) {
+            localeName = localeNameStorage;
+        };
+    }
 
     return SkNEW_ARGS(SkFontMgr_DirectWrite, (sysFontCollection.get(), localeName, localeNameLen));
 }