Implemented ExternalData interface on DownloadItem and used it for SafeBrowsing.

content/browser/download/download_item.cc

 // Copyright (c) 2011 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_item.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/basictypes.h"
 #include "base/file_util.h"
 #include "base/format_macros.h"
 #include "base/i18n/case_conversion.h"
 #include "base/i18n/string_search.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
+#include "base/stl_util.h"
 #include "base/stringprintf.h"
 #include "base/utf_string_conversions.h"
 #include "content/browser/download/download_create_info.h"
 #include "content/browser/download/download_file.h"
 #include "content/browser/download/download_file_manager.h"
 #include "content/browser/download/download_id.h"
 #include "content/browser/download/download_manager.h"
 #include "content/browser/download/download_persistent_store_info.h"
 #include "content/browser/download/download_request_handle.h"
 #include "content/browser/download/download_stats.h"
@@ skipping 199 matching lines @@
       delegate_delayed_complete_(false) {
   Init(true /* actively downloading */);
 }
 
 DownloadItem::~DownloadItem() {
   // TODO(rdsmith): Change to DCHECK after http://crbug.com/85408 resolved.
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   TransitionTo(REMOVING);
   download_manager_->AssertQueueStateConsistent(this);
+  STLDeleteContainerPairSecondPointers(
+      external_data_map_.begin(), external_data_map_.end());
 }
 
 void DownloadItem::AddObserver(Observer* observer) {
   // TODO(rdsmith): Change to DCHECK after http://crbug.com/85408 resolved.
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   observers_.AddObserver(observer);
 }
 
 void DownloadItem::RemoveObserver(Observer* observer) {
@@ skipping 463 matching lines @@
 
 void DownloadItem::OffThreadCancel(DownloadFileManager* file_manager) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   request_handle_->CancelRequest();
 
   BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
                           base::Bind(&DownloadFileManager::CancelDownload,
                                      file_manager, global_id()));
 }
 
+DownloadItem::ExternalData*
+DownloadItem::GetExternalData(void* key) {
+  if (external_data_map_.count(key) == 0)
+    return NULL;
+  return external_data_map_[key];
+}
+
+void DownloadItem::SetExternalData(
+    void* key, DownloadItem::ExternalData* data) {
+  if (external_data_map_.count(key) != 0) {

[noelutz, 2011/11/16 02:59:38]

How about this to avoid all these lookups?

std::map<void*, ExternalData*>::iterator it = ....find(key);
if (it == ...end()) {
  external_data_map_[key] = data;
} else if (it->second != data) {
  delete it->second;
  it->second = data;
}

[Randy Smith (Not in Mondays), 2011/11/18 02:02:57]

Yes, noticeably better.  Thanks for the nudge.  Done.

+    if (external_data_map_[key] == data)
+      return;                           // Nothing to do.
+    delete external_data_map_[key];
+  }
+  external_data_map_[key] = data;
+}
+
 void DownloadItem::Init(bool active) {
   // TODO(rdsmith): Change to DCHECK after http://crbug.com/85408 resolved.
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   UpdateTarget();
   if (active) {
     download_stats::RecordDownloadCount(download_stats::START_COUNT);
   }
   VLOG(20) << __FUNCTION__ << "() " << DebugString(true);
 }
@@ skipping 68 matching lines @@
         state_info_.target_name.value().c_str(),
         full_path().value().c_str());
   } else {
     description += base::StringPrintf(" url = \"%s\"", url_list.c_str());
   }
 
   description += " }";
 
   return description;
 }