Replace __init__ function in asm-wasm-builder with the start function section

src/wasm/asm-wasm-builder.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/v8.h"
 
 // Required to get M_E etc. in MSVC.
 #if defined(_WIN32)
 #define _USE_MATH_DEFINES
 #endif
@@ skipping 48 matching lines @@
         init_function_index_(0),
         next_table_index_(0),
         function_tables_(HashMap::PointersMatch,
                          ZoneHashMap::kDefaultHashMapCapacity,
                          ZoneAllocationPolicy(zone)),
         imported_function_table_(this) {
     InitializeAstVisitor(isolate);
   }
 
   void InitializeInitFunction() {
-    unsigned char init[] = "__init__";
     init_function_index_ = builder_->AddFunction();
     current_function_builder_ = builder_->FunctionAt(init_function_index_);
-    current_function_builder_->SetName(init, 8);
     current_function_builder_->ReturnType(kAstStmt);
-    current_function_builder_->Exported(1);
+    builder_->MarkStartFunction(init_function_index_);
     current_function_builder_ = nullptr;
   }
 
   void Compile() {
     InitializeInitFunction();
     RECURSE(VisitFunctionLiteral(literal_));
   }
 
   void VisitVariableDeclaration(VariableDeclaration* decl) {}
 
@@ skipping 1422 matching lines @@
 // that zone in constructor may be thrown away once wasm module is written.
 WasmModuleIndex* AsmWasmBuilder::Run() {
   AsmWasmBuilderImpl impl(isolate_, zone_, literal_, foreign_, typer_);
   impl.Compile();
   WasmModuleWriter* writer = impl.builder_->Build(zone_);
   return writer->WriteTo(zone_);
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8