[wasm] Implement official wasm text format

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 <memory>
 
 #include "src/api.h"
@@ skipping 372 matching lines @@
 
 // Get the script of the wasm module. If the origin of the module is asm.js, the
 // returned Script will be a JavaScript Script of Script::TYPE_NORMAL, otherwise
 // it's of type TYPE_WASM.
 Handle<Script> GetScript(Handle<JSObject> instance);
 
 // Compute the disassembly of a wasm function.
 // Returns the disassembly string and a list of <byte_offset, line, column>
 // entries, mapping wasm byte offsets to line and column in the disassembly.
 // The list is guaranteed to be ordered by the byte_offset.
+// Returns an empty string and empty vector if the function index is invalid.
 std::pair<std::string, std::vector<std::tuple<uint32_t, int, int>>>
 DisassembleFunction(Handle<WasmCompiledModule> compiled_module, int func_index);
 
 // Get the asm.js source position for the given byte offset in the given
 // function.
 int GetAsmWasmSourcePosition(Handle<JSObject> instance, int func_index,
                              int byte_offset);
 
 V8_EXPORT_PRIVATE MaybeHandle<WasmModuleObject> CreateModuleObjectFromBytes(
     Isolate* isolate, const byte* start, const byte* end, ErrorThrower* thrower,
@@ skipping 42 matching lines @@
 void ValidateModuleState(Isolate* isolate, Handle<WasmModuleObject> module_obj);
 void ValidateOrphanedInstance(Isolate* isolate,
                               Handle<WasmInstanceObject> instance);
 
 }  // namespace testing
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_MODULE_H_