Convert the async device ID getter to a chrome resource host

ppapi/host/ppapi_host.h

Index: ppapi/host/ppapi_host.h
diff --git a/ppapi/host/ppapi_host.h b/ppapi/host/ppapi_host.h
index 3f3605c529875f70837cf1ce23aa2effb7cf60bd..748d47a531884c2497b6e985a18a425ff2e9e634 100644
--- a/ppapi/host/ppapi_host.h
+++ b/ppapi/host/ppapi_host.h
@@ -37,12 +37,11 @@ class ResourceHost;
 // corresponding replies.
 class PPAPI_HOST_EXPORT PpapiHost : public IPC::Sender, public IPC::Listener {
  public:
-  // The sender is the channel to the plugin for outgoing messages. The factory
-  // will be used to receive resource creation messages from the plugin. Both
-  // pointers are owned by the caller and must outlive this class.
-  PpapiHost(IPC::Sender* sender,
-            HostFactory* host_factory,
-            const PpapiPermissions& perms);
+  // The sender is the channel to the plugin for outgoing messages.
+  // Normally the creator will add filters for resource creation messages
+  // (AddHostFactoryFilter) and instance messages (AddInstanceMessageFilter)
+  // after construction.
+  PpapiHost(IPC::Sender* sender, const PpapiPermissions& perms);
   virtual ~PpapiHost();
 
   const PpapiPermissions& permissions() const { return permissions_; }
@@ -57,6 +56,10 @@ class PPAPI_HOST_EXPORT PpapiHost : public IPC::Sender, public IPC::Listener {
   void SendReply(const proxy::ResourceMessageReplyParams& params,
                  const IPC::Message& msg);
 
+  // Adds the given host factory filter to the host. The PpapiHost will take
+  // ownership of the pointer.
+  void AddHostFactoryFilter(scoped_ptr<HostFactory> filter);
+
   // Adds the given message filter to the host. The PpapiHost will take
   // ownership of the pointer.
   void AddInstanceMessageFilter(scoped_ptr<InstanceMessageFilter> filter);
@@ -78,11 +81,14 @@ class PPAPI_HOST_EXPORT PpapiHost : public IPC::Sender, public IPC::Listener {
   // Non-owning pointer.
   IPC::Sender* sender_;
 
-  // Non-owning pointer.
-  HostFactory* host_factory_;
-
   PpapiPermissions permissions_;
 
+  // Filters for resource creation messages. Note that since we don't support
+  // deleting these dynamically we don't need to worry about modifications
+  // during iteration. If we add that capability, this should be replaced with
+  // an ObserverList.
+  ScopedVector<HostFactory> host_factory_filters_;
+
   // Filters for instance messages. Note that since we don't support deleting
   // these dynamically we don't need to worry about modifications during
   // iteration. If we add that capability, this should be replaced with an