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

src/ports/SkFontHost_win_dw.cpp

Index: src/ports/SkFontHost_win_dw.cpp
===================================================================
--- src/ports/SkFontHost_win_dw.cpp	(revision 12947)
+++ src/ports/SkFontHost_win_dw.cpp	(working copy)
@@ -68,6 +68,15 @@
             "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.");