[wasm] Add a magic word and a version number to the binary.

src/wasm/wasm-module.h

 // 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.
 
 #ifndef V8_WASM_MODULE_H_
 #define V8_WASM_MODULE_H_
 
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
 
 #include "src/api.h"
 #include "src/handles.h"
 
 namespace v8 {
 namespace internal {
 
 namespace compiler {
 class CallDescriptor;
 }
 
 namespace wasm {
 const size_t kMaxModuleSize = 1024 * 1024 * 1024;
 const size_t kMaxFunctionSize = 128 * 1024;
 const size_t kMaxStringSize = 256;
+const uint32_t kWasmMagic = 0x6d736100;
+const uint32_t kWasmVersion = 0x0a;
 
 enum WasmSectionDeclCode {
   kDeclMemory = 0x00,
   kDeclSignatures = 0x01,
   kDeclFunctions = 0x02,
   kDeclGlobals = 0x03,
   kDeclDataSegments = 0x04,
   kDeclFunctionTable = 0x05,
   kDeclEnd = 0x06,
   kDeclStartFunction = 0x07,
@@ skipping 214 matching lines @@
 
 // For testing. Decode, verify, and run the last exported function in the
 // given decoded module.
 int32_t CompileAndRunWasmModule(Isolate* isolate, WasmModule* module);
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_MODULE_H_