Work around SkString::gEmptyRec->writable_str() is unwritable.

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 50 matching lines @@
 }
 
 /** Converts a WCHAR string to a utf8 string. */
 static HRESULT wchar_to_skstring(WCHAR* name, SkString* skname) {
     int len = WideCharToMultiByte(CP_UTF8, 0, name, -1, NULL, 0, NULL, NULL);
     if (0 == len) {
         HRM(HRESULT_FROM_WIN32(GetLastError()),
             "Could not get length for utf-8 to wchar conversion.");
     }
     skname->resize(len - 1);
+
+    // TODO: remove after https://code.google.com/p/skia/issues/detail?id=1989 is fixed.
+    // If we resize to 0 then the skname points to gEmptyRec (the unique empty SkString::Rec).
+    // gEmptyRec is static const and on Windows this means the value is in a read only page.
+    // Writing to it in the following call to WideCharToMultiByte will cause an access violation.
+    if (1 == len) {
+        return S_OK;
+    }
+
     len = WideCharToMultiByte(CP_UTF8, 0, name, -1, skname->writable_str(), len, NULL, NULL);
     if (0 == len) {
         HRM(HRESULT_FROM_WIN32(GetLastError()), "Could not convert utf-8 to wchar.");
     }
     return S_OK;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 static void create_dwrite_factory(IDWriteFactory** factory) {
@@ skipping 1822 matching lines @@
         SK_TRACEHR(hr, "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));
 }