Migrate mac installer to delegate-driven model

chrome/installer/mac/app/DownloadDelegate.m

 // 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.
 
 #import <assert.h>
 
 #import "DownloadDelegate.h"
 #import "Downloader.h"
 
 @implementation DownloadDelegate : NSObject

[Sidney San Martín, 2016/07/18 18:28:52]

Not strictly related to this CL, but you probably don't need this class.
Downloader should serve as the NSURLSessionDownloadDelegate.

 
 // Skeleton of delegate method to provide download progress updates.
 // TODO: Make use of (totalBytesWritten/totalBytesExpectedToWrite)*100
 // to generate download progress percentage.
 - (void)URLSession:(NSURLSession*)session
                  downloadTask:(NSURLSessionDownloadTask*)downloadTask
                  didWriteData:(int64_t)bytesWritten
             totalBytesWritten:(int64_t)totalBytesWritten
     totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
 }
 
 // Delegate method to move downloaded disk image to user's Download directory.
 - (void)URLSession:(NSURLSession*)session
                  downloadTask:(NSURLSessionDownloadTask*)downloadTask
     didFinishDownloadingToURL:(NSURL*)location {
   assert([location isFileURL]);
   NSFileManager* manager = [[NSFileManager alloc] init];
   NSURL* downloadsDirectory =
       [[NSURL alloc] initFileURLWithPath:[Downloader getDownloadsFilePath]];
   if ([manager fileExistsAtPath:location.path]) {
     [manager copyItemAtURL:location toURL:downloadsDirectory error:nil];

[Sidney San Martín, 2016/07/18 18:28:52]

You should probably move the file, not copy it — else the downloaded copy will
hang out until the system cleans it up (e.g. on the next restart).

   } else {
     // TODO: Error Handling
   }
 }
 
 - (void)URLSession:(NSURLSession*)session
                     task:(NSURLSessionTask*)task
     didCompleteWithError:(NSError*)error {
   // TODO: Error Handling
+
+  // TODO: indicate that the program keeps running from here?! lol
 }
 @end