[wasm] Refactor import handling for 0xC.

test/mjsunit/wasm/gc-stress.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  --stress-gc
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+function run(f) {
+  var builder = new WasmModuleBuilder();
+  builder.addImport("f", kSig_i_i);
+  builder.addFunction("main", kSig_i_i)
+    .addBody([
+      kExprGetLocal, 0,
+      kExprCallFunction, 0])
+    .exportAs("main");
+
+  print("module");
+  var module = new WebAssembly.Module(builder.toBuffer());
+
+  for (var i = 0; i < 10; i++) {
+    print("  instance " + i);
+    var instance = new WebAssembly.Instance(module, {f: f});
+    var g = instance.exports.main;
+    for (var j = 0; j < 10; j++) {
+      assertEquals(f(j), g(j));
+    }
+  }
+}
+
+(function test() {
+  for (var i = 0; i < 100; i++) {
+    run(x => (x + 19));
+    run(x => (x - 18));
+  }
+})();