[wasm] Wrap start function in a JS->WASM wrapper before calling it during initialization.

test/mjsunit/wasm/start-function.js

 // Copyright 2016 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.
 
 // Flags: --expose-wasm
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 function instantiate(sig, body) {
@@ skipping 44 matching lines @@
   var func = builder.addFunction("", kSig_v_v)
     .addBody([kExprNop]);
 
   builder.addExplicitSection([kStartSectionCode, 0]);
   builder.addExplicitSection([kStartSectionCode, 0]);
 
   assertThrows(builder.instantiate);
 })();
 
 
-(function testRun() {
-  print("testRun");
+(function testRun1() {
+  print("testRun1");
   var builder = new WasmModuleBuilder();
 
   builder.addMemory(12, 12, true);
 
   var func = builder.addFunction("", kSig_v_v)
-    .addBody([kExprI8Const, 0, kExprI8Const, 77, kExprI32StoreMem, 0, 0]);
+    .addBody([kExprI8Const, 0, kExprI8Const, 66, kExprI32StoreMem, 0, 0]);
 
   builder.addStart(func.index);
 
+  var module = builder.instantiate();
+  var memory = module.exports.memory.buffer;
+  var view = new Int8Array(memory);
+  assertEquals(66, view[0]);
+})();
+
+(function testRun2() {
+  print("testRun2");
+  var builder = new WasmModuleBuilder();
+
+  builder.addMemory(12, 12, true);
+
+  var func = builder.addFunction("", kSig_v_v)
+    .addBody([kExprI8Const, 0, kExprI8Const, 22, kExprI8Const, 55, kExprI32Add, kExprI32StoreMem, 0, 0]);
+
+  builder.addStart(func.index);
+
   var module = builder.instantiate();
   var memory = module.exports.memory.buffer;
   var view = new Int8Array(memory);
   assertEquals(77, view[0]);
 })();
 
 (function testStartFFI() {
   print("testStartFFI");
   var ranned = false;
   var ffi = { foo : function() {
     print("we ranned at stert!");
     ranned = true;
   }};
 
   var builder = new WasmModuleBuilder();
   var sig_index = builder.addType(kSig_v_v);
 
   builder.addImport("foo", sig_index);
   var func = builder.addFunction("", sig_index)
     .addBody([kExprCallFunction, 0]);
 
   builder.addStart(func.index);
 
   var module = builder.instantiate(ffi);
   assertTrue(ranned);
 })();