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

test/mjsunit/wasm/instance-memory-gc-stress.js

Index: test/mjsunit/wasm/instance-memory-gc-stress.js
diff --git a/test/mjsunit/wasm/instance-memory-gc-stress.js b/test/mjsunit/wasm/instance-memory-gc-stress.js
index fc824c2af7e56fe5d3cd29436249bc2c03f4b885..64909eb9dff4e0075b26ca0b0ec4dee25239cd1b 100644
--- a/test/mjsunit/wasm/instance-memory-gc-stress.js
+++ b/test/mjsunit/wasm/instance-memory-gc-stress.js
@@ -13,7 +13,7 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   print("InstanceMemoryGcStress");
   let memory = new WebAssembly.Memory({initial: 100, maximum: 1500});
   var builder = new WasmModuleBuilder();
-  builder.addImportedMemory("imported_mem");
+  builder.addImportedMemory("mod", "imported_mem");
   builder.addFunction("mem_size", kSig_i_v)
     .addBody([kExprMemorySize, kMemoryZero])
     .exportFunc();
@@ -23,7 +23,7 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   var instances = [];
   for (var i = 0; i < 5; i++) {
     gc();
-    instances.push(builder.instantiate({imported_mem: memory}));
+    instances.push(builder.instantiate({mod: {imported_mem: memory}}));
   }
   function grow_instance_0(pages) { return instances[0].exports.grow(pages); }
   function grow_instance_1(pages) { return instances[1].exports.grow(pages); }
@@ -60,7 +60,7 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   assertEquals(800, instances[0].exports.mem_size());
 
   // Instantiate a new instance and verify that it can be grown correctly.
-  instances.push(builder.instantiate({imported_mem: memory}));
+  instances.push(builder.instantiate({mod: {imported_mem: memory}}));
   function grow_instance_5(pages) { return instances[5].exports.grow(pages); }
   gc();
   gc();