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

test/mjsunit/wasm/instance-memory-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 --expose-gc
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
 // This test verifies that when instances are exported, Gc'ed, the other
 // instances in the chain still maintain a consistent view of the memory.
 (function InstanceMemoryGcStress() {
   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();
   builder.addFunction("grow", kSig_i_i)
     .addBody([kExprGetLocal, 0, kExprGrowMemory, kMemoryZero])
     .exportFunc();
   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); }
   function grow_instance_2(pages) { return instances[2].exports.grow(pages); }
   function grow_instance_3(pages) { return instances[3].exports.grow(pages); }
   function grow_instance_4(pages) { return instances[4].exports.grow(pages); }
 
   var start_index = 0;
   var end_index = 5;
   function verify_mem_size(expected_pages) {
@@ skipping 16 matching lines @@
   // i[0] - i[2] - i[3] - i[4]
   start_index = 2;
   verify_mem_size(600);
   assertEquals(600, instances[0].exports.mem_size());
   assertEquals(600, grow_instance_2(200));
   assertEquals(800*kPageSize, memory.buffer.byteLength);
   verify_mem_size(800);
   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();
 
   // i[0] - i[2] - i[3] - i[4] - i[5]
   start_index = 2;
   end_index = 6;
   verify_mem_size(800);
   assertEquals(800, instances[0].exports.mem_size());
   assertEquals(800, grow_instance_2(100));
@@ skipping 41 matching lines @@
   assertEquals(1100, instances[2].exports.mem_size());
   assertEquals(1100, instances[5].exports.mem_size());
   assertEquals(1100, grow_instance_5(1));
   gc();
   gc();
 
   assertEquals(1101*kPageSize, memory.buffer.byteLength);
   assertEquals(1101, instances[2].exports.mem_size());
   assertEquals(1101, instances[5].exports.mem_size());
 })();