Ensure that just started broker doesn't get events addressed to dead instance.

ceee/ie/broker/broker_rpc_lib.idl

 import "oaidl.idl";
 import "ocidl.idl";
 
 [ 
   uuid (931C5D3F-A6D7-411B-98ED-789FC9291302),
   // TODO(vitalybuka@google.com): decide if we need meaningful version.
   version(1.1),
   pointer_default(unique),
 ]
 interface CeeeBroker {
 
 // Context handle to allow server maintain number of active clients.
 typedef [context_handle] void* BrokerContextHandle;
 
 // @name Implementation specific calls.
 // @{
 // Returns context handle for new client.
 BrokerContextHandle Connect( 
     [in] handle_t binding_handle);
 
 // Release context handle.
 void Disconnect( 
     [in] handle_t binding_handle,
     [in, out] BrokerContextHandle* context);
 // @}
 
 // @name Remote calls.
 // @{
 // Fires event to broker.
+// @param context is required to avoid execution by wrong broker instance.
 void FireEvent(
     [in] handle_t binding_handle,
+    [in] BrokerContextHandle context,
     [in, string] const char* event_name,
     [in, string] const char* event_args);
 
 void SendUmaHistogramTimes(
     [in] handle_t binding_handle,
     [in, string] const char* name,
     [in] int sample);
 
 void SendUmaHistogramData(
     [in] handle_t binding_handle,
     [in, string] const char* name,
     [in] int sample,
     [in] int min,
     [in] int max,
     [in] int bucket_count);
 // @}
 }
 
 // This dummy library statement enforces the creation of a history_indexer.tlb.
 // This is necessary since MSVC assumes a .idl always creates a .tlb. Otherwise,
 // this .idl is always recompiled, giving many engs a headache.
 [
   uuid(B696C552-D640-4756-BE75-B86BE2AEB6C7),
   helpstring("Dummy library")
 ]
 library broker_rcp_lib
 {
 };