[wasm] Add a flag to generate an mjsunit test out of a wasm-code fuzzer test case.

src/wasm/ast-decoder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/signature.h"
 
 #include "src/bit-vector.h"
 #include "src/flags.h"
 #include "src/handles.h"
 #include "src/zone/zone-containers.h"
@@ skipping 363 matching lines @@
         base_(body.base),
         local_type_vec_(zone),
         stack_(zone),
         control_(zone),
         last_end_found_(false),
         current_catch_(kNullCatch) {
     local_types_ = &local_type_vec_;
   }
 
   bool Decode() {
+    if (FLAG_wasm_code_generate_test) {
+      PrintAstForDebugging(start_, end_);
+    }
     base::ElapsedTimer decode_timer;
     if (FLAG_trace_wasm_decode_time) {
       decode_timer.Start();
     }
     stack_.clear();
     control_.clear();
 
     if (end_ < pc_) {
       error("function body end < start");
       return false;
@@ skipping 1527 matching lines @@
 
   // Print the function signature.
   if (body.sig) {
     os << "// signature: " << *body.sig << std::endl;
     ++line_nr;
   }
 
   // Print the local declarations.
   AstLocalDecls decls(&zone);
   BytecodeIterator i(body.start, body.end, &decls);
-  if (body.start != i.pc()) {
+  if (body.start != i.pc() && !FLAG_wasm_code_generate_test) {
     os << "// locals: ";
     for (auto p : decls.local_types) {
       LocalType type = p.first;
       uint32_t count = p.second;
       os << " " << count << " " << WasmOpcodes::TypeName(type);
     }
     os << std::endl;
     ++line_nr;
 
     for (const byte* locals = body.start; locals < i.pc(); locals++) {
@@ skipping 93 matching lines @@
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end) {
   FunctionBody body = {nullptr, nullptr, nullptr, start, end};
   WasmFullDecoder decoder(zone, nullptr, body);
   return decoder.AnalyzeLoopAssignmentForTesting(start, num_locals);
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8