[wasm] Provide better stack traces for asm.js code

src/wasm/module-decoder.h

Index: src/wasm/module-decoder.h
diff --git a/src/wasm/module-decoder.h b/src/wasm/module-decoder.h
index 1e2b32a23c45f296e82eefcd30ec3e439ad3abd2..faaba1251f8d8d1d11d5637152b6cec92d7ec473 100644
--- a/src/wasm/module-decoder.h
+++ b/src/wasm/module-decoder.h
@@ -17,6 +17,8 @@ typedef Result<const WasmModule*> ModuleResult;
 typedef Result<WasmFunction*> FunctionResult;
 typedef std::vector<std::pair<int, int>> FunctionOffsets;
 typedef Result<FunctionOffsets> FunctionOffsetsResult;
+typedef std::vector<std::vector<std::pair<int, int>>> AsmJsOffsets;
+typedef Result<AsmJsOffsets> AsmJsOffsetsResult;
 
 // Decodes the bytes of a WASM module between {module_start} and {module_end}.
 V8_EXPORT_PRIVATE ModuleResult DecodeWasmModule(Isolate* isolate, Zone* zone,
@@ -45,6 +47,15 @@ FunctionOffsetsResult DecodeWasmFunctionOffsets(
 
 WasmInitExpr DecodeWasmInitExprForTesting(const byte* start, const byte* end);
 
+// Extracts the mapping from wasm byte offset to asm.js source position per
+// function.
+// Returns a vector of vectors with <byte_offset, source_position> entries, or
+// failure if the wasm bytes are detected as invalid. Note that this validation
+// is not complete.
+AsmJsOffsetsResult DecodeAsmJsOffsets(const byte* module_start,
+                                      const byte* module_end,
+                                      uint32_t num_imported_functions);
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8