Make down-conversion explicit from CFX_Widetring to CFX_WideStringC.

testing/libfuzzer/pdf_fm2js_fuzzer.cc

Index: testing/libfuzzer/pdf_fm2js_fuzzer.cc
diff --git a/testing/libfuzzer/pdf_fm2js_fuzzer.cc b/testing/libfuzzer/pdf_fm2js_fuzzer.cc
index 569c1291af3de022b028405ee525a8ed69626438..0a5f6d64ae248dea8de0a6602e3f1a72970f4468 100644
--- a/testing/libfuzzer/pdf_fm2js_fuzzer.cc
+++ b/testing/libfuzzer/pdf_fm2js_fuzzer.cc
@@ -16,7 +16,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   CFX_WideString input = CFX_WideString::FromUTF8(
       reinterpret_cast<const char*>(data), static_cast<FX_STRSIZE>(size));
   CXFA_FMProgram program;
-  if (program.Init(input) || program.ParseProgram())
+  if (program.Init(input.AsWideStringC()) || program.ParseProgram())
     return 0;
 
   CFX_WideTextBuf js;