Bug 643649. Pass correct parameter value into registry call. r=joedrew

gfx/thebes/gfxDWriteFontList.cpp

@@ -1011,7 +1011,7 @@ gfxDWriteFontList::GetFontSubstitutes()
 
     for (i = 0, rv = ERROR_SUCCESS; rv != ERROR_NO_MORE_ITEMS; i++) {
         aliasName[0] = 0;
-        lenAlias = sizeof(aliasName);
+        lenAlias = NS_ARRAY_LENGTH(aliasName);
         actualName[0] = 0;
         lenActual = sizeof(actualName);
         rv = RegEnumValueW(hKey, i, aliasName, &lenAlias, NULL, &valueType, 

gfx/thebes/gfxGDIFontList.cpp

@@ -626,7 +626,7 @@ gfxGDIFontList::GetFontSubstitutes()
 
     for (i = 0, rv = ERROR_SUCCESS; rv != ERROR_NO_MORE_ITEMS; i++) {
         aliasName[0] = 0;
-        lenAlias = sizeof(aliasName);
+        lenAlias = NS_ARRAY_LENGTH(aliasName);
         actualName[0] = 0;
         lenActual = sizeof(actualName);
         rv = RegEnumValueW(hKey, i, aliasName, &lenAlias, NULL, &valueType,