[wasm] Support a two-level namespace for imports.

test/mjsunit/wasm/test-wasm-module-builder.js

Index: test/mjsunit/wasm/test-wasm-module-builder.js
diff --git a/test/mjsunit/wasm/test-wasm-module-builder.js b/test/mjsunit/wasm/test-wasm-module-builder.js
index e68e375f54fb66470122b6b56f61facf46779e4e..8103d7b9bad457a8d0fccca5d39dd56d71096878 100644
--- a/test/mjsunit/wasm/test-wasm-module-builder.js
+++ b/test/mjsunit/wasm/test-wasm-module-builder.js
@@ -138,3 +138,16 @@ var debug = false;
     var instance = Wasm.instantiateModule(array2);
     assertEquals(17, instance.exports.blarg());
 })();
+
+(function ImportTestTwoLevel() {
+    var module = new WasmModuleBuilder();
+    var index = module.addImportWithModule("mod", "print", [kAstStmt, kAstI32]);
+    module.addFunction("foo", [kAstStmt])
+        .addBody([kExprCallImport, index, kExprI8Const, 19])
+        .exportAs("main");
+
+    var buffer = module.toBuffer(debug);
+    var instance = Wasm.instantiateModule(buffer, {mod: {print: print}});
+    print("should print 19! ");
+    instance.exports.main();
+})();