downloads: add the ability to undo download removal.

content/browser/download/download_manager_impl.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/download/download_manager_impl.h"
 
 #include <iterator>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 227 matching lines @@
       shutdown_needed_(true),
       browser_context_(browser_context),
       delegate_(NULL),
       net_log_(net_log),
       weak_factory_(this) {
   DCHECK(browser_context);
 }
 
 DownloadManagerImpl::~DownloadManagerImpl() {
   DCHECK(!shutdown_needed_);
+  DCHECK(removed_downloads_.empty());

[Dan Beam, 2014/11/19 23:16:26]

I could change this to:

  STLDeleteValues(&removed_downloads_);

if you want... but it shouldn't ever be necessary assuming all
DownloadsDomHandlers go down before this class

 }
 
 DownloadItemImpl* DownloadManagerImpl::CreateActiveItem(
     uint32 id, const DownloadCreateInfo& info) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(!ContainsKey(downloads_, id));
   net::BoundNetLog bound_net_log =
       net::BoundNetLog::Make(net_log_, net::NetLog::SOURCE_DOWNLOAD);
   DownloadItemImpl* download =
       item_factory_->CreateActiveItem(this, id, info, bound_net_log);
@@ skipping 80 matching lines @@
   // dangerous downloads which will remain in history if they aren't explicitly
   // accepted or discarded. Canceling will remove the intermediate download
   // file.
   for (DownloadMap::iterator it = downloads_.begin(); it != downloads_.end();
        ++it) {
     DownloadItemImpl* download = it->second;
     if (download->GetState() == DownloadItem::IN_PROGRESS)
       download->Cancel(false);
   }
   STLDeleteValues(&downloads_);
-  downloads_.clear();

[Dan Beam, 2014/11/19 23:16:26]

STLDeleteValues() does this already

 
   // We'll have nothing more to report to the observers after this point.
   observers_.Clear();
 
   if (delegate_)
     delegate_->Shutdown();
   delegate_ = NULL;
 }
 
 void DownloadManagerImpl::StartDownload(
@@ skipping 197 matching lines @@
   return file_factory_.get();
 }
 
 void DownloadManagerImpl::DownloadRemoved(DownloadItemImpl* download) {
   if (!download)
     return;
 
   uint32 download_id = download->GetId();
   if (downloads_.erase(download_id) == 0)
     return;
-  delete download;
+
+  removed_downloads_[download_id] = download;
 }
 
 int DownloadManagerImpl::RemoveDownloadsBetween(base::Time remove_begin,
                                                 base::Time remove_end) {
   int count = 0;
   DownloadMap::const_iterator it = downloads_.begin();
   while (it != downloads_.end()) {
     DownloadItemImpl* download = it->second;
 
     // Increment done here to protect against invalidation below.
@@ skipping 14 matching lines @@
   return RemoveDownloadsBetween(remove_begin, base::Time());
 }
 
 int DownloadManagerImpl::RemoveAllDownloads() {
   // The null times make the date range unbounded.
   int num_deleted = RemoveDownloadsBetween(base::Time(), base::Time());
   RecordClearAllSize(num_deleted);
   return num_deleted;
 }
 
+void DownloadManagerImpl::ReviveDownload(uint32 id) {
+  auto it = removed_downloads_.find(id);
+  if (it == removed_downloads_.end())
+    return;
+
+  DownloadItemImpl* item = removed_downloads_[id];
+  removed_downloads_.erase(it);
+
+  downloads_[id] = item;
+
+  FOR_EACH_OBSERVER(Observer, observers_, OnDownloadRevived(this, item));
+  FOR_EACH_OBSERVER(Observer, observers_, OnDownloadCreated(this, item));

[benjhayden, 2014/11/21 00:50:01]

Is every listener really ok with having a single item created more than once?

[Dan Beam, 2014/11/21 05:32:21]

According to my interpretation of the documentation, yes.

"this method may be called an arbitrary number of times"

https://code.google.com/p/chromium/codesearch#chromium/src/content/public/bro...

+}
+
+void DownloadManagerImpl::FinalizeRemoval(uint32 id) {
+  auto it = removed_downloads_.find(id);
+  if (it == removed_downloads_.end())
+    return;
+
+  delete it->second;
+  removed_downloads_.erase(it);
+}
+
 void DownloadManagerImpl::DownloadUrl(
     scoped_ptr<DownloadUrlParameters> params) {
   if (params->post_id() >= 0) {
     // Check this here so that the traceback is more useful.
     DCHECK(params->prefer_cache());
     DCHECK_EQ("POST", params->method());
   }
   BrowserThread::PostTask(BrowserThread::IO, FROM_HERE, base::Bind(
       &BeginDownload, base::Passed(&params),
       content::DownloadItem::kInvalidId));
@@ skipping 106 matching lines @@
   if (delegate_)
     delegate_->OpenDownload(download);
 }
 
 void DownloadManagerImpl::ShowDownloadInShell(DownloadItemImpl* download) {
   if (delegate_)
     delegate_->ShowDownloadInShell(download);
 }
 
 }  // namespace content