Migrate mac installer to delegate-driven model

chrome/installer/mac/app/OmahaCommunication.h

 // Copyright 2016 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 CHROME_INSTALLER_MAC_APP_OMAHACOMMUNICATION_H_
 #define CHROME_INSTALLER_MAC_APP_OMAHACOMMUNICATION_H_
 
 #import <Foundation/Foundation.h>
 
-#include "NetworkCommunication.h"
+#import "NetworkCommunication.h"
 
-typedef void (^OmahaRequestCompletionHandler)(NSData*, NSError*);
+@protocol OmahaCommunicationDelegate
+- (void)onOmahaSuccessWithResponseBody:(NSData*)responseBody
+                              AndError:(NSError*)error;
+@end
 
-@interface OmahaCommunication : NSObject
+@interface OmahaCommunication : NSObject<NSURLSessionDataDelegate> {
+  id<OmahaCommunicationDelegate> _delegate;
+}
 
 @property(nonatomic, copy) NSXMLDocument* requestXMLBody;
+// TODO: talk to @sdy about use of NetworkCommunication
 @property(nonatomic, copy) NetworkCommunication* sessionHelper;
+@property(nonatomic, assign) id<OmahaCommunicationDelegate> delegate;
 
 - (id)init;
 - (id)initWithBody:(NSXMLDocument*)xmlBody;
 
 // Sends the request created using the session helper.
-- (void)sendRequestWithBlock:(OmahaRequestCompletionHandler)block;
+- (void)sendRequest;
 
 @end
 
 #endif  // CHROME_INSTALLER_MAC_APP_OMAHACOMMUNICATION_H_