Adding the Copresence RpcHandler and HttpPost helper.

components/copresence/proto/rpcs.proto

 syntax = "proto2";
 package copresence;
 option optimize_for = LITE_RUNTIME;
 import "codes.proto";
 import "enums.proto";
 import "data.proto";
 message RequestHeader {
-  optional DeviceRegistration device_id = 3 [deprecated = true];
   optional ClientVersion client_version = 4;
   optional ClientVersion framework_version = 5;
   optional int64 current_time_millis = 6;
   optional string registered_device_id = 7;
   repeated string experiment_override = 8;
   optional string configuration_etag = 11;
-  extensions 9 to 9;
 }
 message ResponseHeader {
-  optional ErrorType error_type = 1 [deprecated = true];
   optional DebugInfo debug_info = 2;
   optional Status status = 3;
 }
 message RegisterDeviceRequest {
   optional RequestHeader header = 1;
-  optional DeviceRegistration old_registration = 2 [deprecated = true];
-  optional DeviceRegistration new_registration = 3 [deprecated = true];
   optional PushServiceRegistration push_service = 5;
   optional DeviceIdentifiers device_identifiers = 6;
 }
 message RegisterDeviceResponse {
   optional ResponseHeader header = 1;
   optional string registered_device_id = 2;
 }
 message ReportRequest {
   optional RequestHeader header = 1;
   optional ManageMessagesRequest manage_messages_request = 2;
   optional ManageSubscriptionsRequest manage_subscriptions_request = 3;
   optional UpdateSignalsRequest update_signals_request = 4;
 }
 message UpdateSignalsRequest {
   repeated TokenObservation token_observation = 1;
   optional DeviceState state = 3;
 }
 message ManageMessagesRequest {
   repeated PublishedMessage message_to_publish = 1;
   repeated string id_to_unpublish = 2;
-  optional DeleteAll delete_all = 3;
 }
 message ManageSubscriptionsRequest {
   repeated Subscription subscription = 1;
   repeated string id_to_unsubscribe = 2;
-  optional DeleteAll delete_all = 3;
 }
 message ReportResponse {
   optional ResponseHeader header = 1;
   optional ManageMessagesResponse manage_messages_response = 2;
   optional ManageSubscriptionsResponse manage_subscriptions_response = 3;
   optional UpdateSignalsResponse update_signals_response = 4;
 }
 message UpdateSignalsResponse {
   optional util.error.Code status = 1;
   repeated Token token = 2;
   repeated SubscribedMessage message = 3;
   repeated Directive directive = 4;
 }
 message ManageMessagesResponse {
   optional util.error.Code status = 1;
   repeated MessageResult published_message_result = 3;
-  extensions 2 to 2;
 }
 message ManageSubscriptionsResponse {
   optional util.error.Code status = 1;
   repeated SubscriptionResult subscription_result = 3;
-  extensions 2 to 2;
 }