[wasm] Implement correct 2-level namespace for imports.

test/debugger/debug/wasm/frame-inspection.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
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 Debug = debug.Debug
@@ skipping 30 matching lines @@
   } catch (e) {
     exception = e;
   }
 };
 
 var builder = new WasmModuleBuilder();
 
 // wasm_1 calls wasm_2 on offset 2.
 // wasm_2 calls call_debugger on offset 1.
 
-builder.addImport('func', kSig_v_v);
+builder.addImport("mod", 'func', kSig_v_v);
 
 builder.addFunction('wasm_1', kSig_v_v)
     .addBody([kExprNop, kExprCallFunction, 2])
     .exportAs('main');
 
 builder.addFunction('wasm_2', kSig_v_v).addBody([kExprCallFunction, 0]);
 
 function call_debugger() {
   debugger;
 }
 
-var module = builder.instantiate({func: call_debugger});
+var module = builder.instantiate({mod: {func: call_debugger}});
 
 (function testFrameInspection() {
   Debug.setListener(listener);
   module.exports.main();
   Debug.setListener(null);
 
   assertEquals(1, break_count);
   if (exception) throw exception;
 })();