Preliminary Harmony weak maps API implementation.

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index f9652769886c91333542e3a268f3728fed334310..383717e605fe63d2cbbecd1e0a6b366efe57d471 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -635,6 +635,36 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_Fix) {
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapCreate) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 1);
+  CONVERT_ARG_CHECKED(JSWeakMap, weakmap, 0);
+  Handle<ObjectHashTable> table = isolate->factory()->NewObjectHashTable(0);
+  weakmap->set_table(*table);
+  return *weakmap;
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapGet) {
+  ASSERT(args.length() == 2);
+  CONVERT_ARG_CHECKED(JSWeakMap, weakmap, 0);
+  CONVERT_ARG_CHECKED(JSObject, key, 1);
+  Handle<ObjectHashTable> table(weakmap->table());
+  return table->Lookup(*key);
+}
+
+
+RUNTIME_FUNCTION(MaybeObject*, Runtime_WeakMapSet) {
+  ASSERT(args.length() == 3);
+  CONVERT_ARG_CHECKED(JSWeakMap, weakmap, 0);
+  CONVERT_ARG_CHECKED(JSObject, key, 1);
+  Handle<Object> value(args[2]);
+  Handle<ObjectHashTable> table(weakmap->table());
+  weakmap->set_table(*PutIntoObjectHashTable(table, key, value));
+  return *value;
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_ClassOf) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);