HostResolver is exposed to plugin.

ppapi/shared_impl/private/ppb_host_resolver_shared.h

Index: ppapi/shared_impl/private/ppb_host_resolver_shared.h
diff --git a/ppapi/shared_impl/private/ppb_host_resolver_shared.h b/ppapi/shared_impl/private/ppb_host_resolver_shared.h
new file mode 100644
index 0000000000000000000000000000000000000000..e5710d2592aab4daab3fc0d4936a322d21620124
--- /dev/null
+++ b/ppapi/shared_impl/private/ppb_host_resolver_shared.h
@@ -0,0 +1,71 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef PPAPI_SHARED_IMPL_PRIVATE_PPB_HOST_RESOLVER_SHARED_H_
+#define PPAPI_SHARED_IMPL_PRIVATE_PPB_HOST_RESOLVER_SHARED_H_
+
+#include <string>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "ppapi/shared_impl/private/network_list.h"
+#include "ppapi/shared_impl/resource.h"
+#include "ppapi/shared_impl/tracked_callback.h"
+#include "ppapi/thunk/ppb_host_resolver_private_api.h"
+
+namespace ppapi {
+
+class PPAPI_SHARED_EXPORT PPB_HostResolver_Shared
+    : public thunk::PPB_HostResolver_Private_API,
+      public Resource {
+ public:
+  // C-tor used in Impl case.
+  explicit PPB_HostResolver_Shared(PP_Instance instance);
+
+  // C-tor used in Proxy case.
+  explicit PPB_HostResolver_Shared(const HostResource& resource);
+
+  virtual ~PPB_HostResolver_Shared();
+
+  // Resource overrides.
+  virtual PPB_HostResolver_Private_API*
+      AsPPB_HostResolver_Private_API() OVERRIDE;
+
+  // PPB_HostResolver_Private_API implementation.
+  virtual int32_t Resolve(const char* host,
+                          uint16_t port,
+                          const PP_HostResolver_Private_Hint* hint,
+                          PP_CompletionCallback callback) OVERRIDE;
+  virtual uint32_t GetSize() OVERRIDE;
+  virtual bool GetItem(uint32_t index,
+                       PP_Var* canonical_name,
+                       PP_NetAddress_Private* address) OVERRIDE;
+
+  void OnResolveCompleted(bool succeeded,
+                          const NetworkList& network_list);
+
+  // Send functions that need to be implemented differently for the
+  // proxied and non-proxied derived classes.
+  virtual void SendResolve(const std::string& host,
+                           uint16_t port,
+                           const PP_HostResolver_Private_Hint* hint) = 0;
+
+ protected:
+  static uint32 GenerateHostResolverID();
+
+  const uint32 host_resolver_id_;
+
+  bool resolve_in_progress_;

[yzshen1, 2012/02/28 08:29:00]

It seems you don't need resolve_in_progress_:
TrackedCallback::IsPending(resolve_callback_) <==> resolve_in_progress_.

[ygorshenin1, 2012/02/28 12:09:47]

Done.

+  scoped_refptr<TrackedCallback> resolve_callback_;
+
+  NetworkList network_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(PPB_HostResolver_Shared);
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_PRIVATE_PPB_HOST_RESOLVER_SHARED_H_