Add command line flags to dump asm.js -> wasm conversion data.

src/wasm/wasm-js.cc

Index: src/wasm/wasm-js.cc
diff --git a/src/wasm/wasm-js.cc b/src/wasm/wasm-js.cc
index 663e4b56b1b07975b61aba64a7e7d67ef7fde33a..62a2676032e5096f63921605205d403795a85666 100644
--- a/src/wasm/wasm-js.cc
+++ b/src/wasm/wasm-js.cc
@@ -126,6 +126,15 @@ v8::internal::wasm::WasmModuleIndex* TranslateAsmModule(
   auto module = v8::internal::wasm::AsmWasmBuilder(
                     info->isolate(), info->zone(), info->literal(), foreign)
                     .Run();
+
+  if (i::FLAG_dump_asmjs_wasm) {
+    FILE* wasm_file = fopen(i::FLAG_asmjs_wasm_dumpfile, "wb");
+    if (wasm_file) {
+      fwrite(module->Begin(), module->End() - module->Begin(), 1, wasm_file);
+      fclose(wasm_file);
+    }
+  }
+
   return module;
 }