Make the UI an observer of downloads.

chrome/browser/download/download_ui_controller.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 "chrome/browser/download/download_ui_controller.h"
+
+#include "base/stl_util.h"
+#include "chrome/browser/download/download_item_model.h"
+#include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/browser_tabstrip.h"
+#include "content/public/browser/download_item.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_delegate.h"
+
+#if defined(OS_ANDROID)
+#include "content/public/browser/android/download_controller_android.h"
+#else
+#include "chrome/browser/ui/blocked_content/blocked_content_tab_helper.h"
+#include "chrome/browser/ui/blocked_content/blocked_content_tab_helper_delegate.h"
+#endif
+
+DownloadUIController::DownloadUIController(Profile* profile,
+                                           content::DownloadManager* manager)
+    : ALLOW_THIS_IN_INITIALIZER_LIST(notifier_(manager, this)),
+      profile_(profile) {
+}
+
+DownloadUIController::~DownloadUIController() {
+}
+
+void DownloadUIController::OnDownloadCreated(content::DownloadManager* manager,
+                                             content::DownloadItem* item) {
+  // If this isn't a new download, there's nothing to do.
+  if (!item->IsInProgress())
+    return;
+
+  DownloadItemModel(item).SetShouldNotifyUI(true);
+  // SavePackage downloads are created in a state where they can be shown
+  // immediately in the browser.
+  OnDownloadUpdated(manager, item);
+}
+
+void DownloadUIController::OnDownloadUpdated(content::DownloadManager* manager,
+                                             content::DownloadItem* item) {
+
+  // Ignore if we've already notified the UI about |item| or if it isn't a new
+  // download.
+  if (!DownloadItemModel(item).ShouldNotifyUI())
+    return;
+
+  // Wait until the target path is determined.
+  if (item->GetTargetFilePath().empty())
+    return;
+
+  // For a download that is in-progress, wait until the intermediate rename is
+  // complete.

[Randy Smith (Not in Mondays), 2012/12/20 23:09:25]

What's the goal here?  And isn't it true that the full path is always set after
the target path, so this test renders the above test redundant?

(This comment may be equivalent to "can you flesh out the TODO() so that someone
beside you could read it and have the background to execute it?")

[asanka, 2012/12/20 23:56:19]

I suppose the TODO wasn't a giveaway.
No. The FullPath() isn't set for downloads that are interrupted before/during
the initial rename.

We are filtering for:
- In progress downloads:
  These are shown after they are successfully renamed to the intermediate name
(Both GetTargetFilePath() and GetFullPath() are non-empty and InProgress() is
true).

*and*

- Interrupted downloads that started out in-progress:
  These are shown after the target name is determined so that we have a name to
show for the download. If the initial rename fails, GetTargetFilePath() would be
non-empty, while GetFullPath() is empty.

Why not just show downloads after the the target is determined? That's where I'd
like to go, but I didn't want to make that change until all the callers of
GetFullPath() have been removed from chrome/browser/ui. Currently it's used to
wire up drag&drop, which doesn't affect interrupted downloads.
Right. Perhaps doing the TODO before this CL would be easier. I'll actually do
that instead.

[asanka, 2013/01/10 22:12:14]

https://codereview.chromium.org/11801022/. I'm changing this CL to just wait
until the target determination is complete.

+  // TODO(asanka): Get rid of remaining users of GetFullPath() in ui/.
+  if (item->IsInProgress() && item->GetFullPath().empty())
+    return;
+
+  // At this point, we expect that the download is either interrupted, or
+  // in-progress and the path is known.

[Randy Smith (Not in Mondays), 2012/12/20 23:09:25]

What happens if the download is interrupted before we determine the target file
name?  We never see it?

[asanka, 2012/12/20 23:56:19]

Target name determination happens in chrome/. If the download is interrupted, we
wait until the name is determined and then show the interrupted download.

+
+  // Can't be complete. That would imply that we didn't receive an
+  // OnDownloadUpdated() after the intermediate rename was completed.
+  DCHECK(!item->IsComplete());
+
+  DownloadItemModel(item).SetShouldNotifyUI(false);
+  NotifyDownloadStarting(item);
+}
+
+void DownloadUIController::NotifyDownloadStarting(content::DownloadItem* item) {
+#if defined(OS_ANDROID)
+  // GET downloads are delegated to the Android DownloadManager. Chrome is only
+  // responsible for POST downloads.  See
+  // ChromeWebContentsDelegateAndroid::CanDownload().
+  content::DownloadControllerAndroid::Get()->OnPostDownloadStarted(item);
+#else
+  content::WebContents* web_contents = item->GetWebContents();
+
+  // If the tab requesting the download is a constrained popup that is not
+  // shown, treat the request as if it came from the parent.
+  if (web_contents != NULL) {
+    BlockedContentTabHelper* blocked_content_tab_helper =
+        BlockedContentTabHelper::FromWebContents(web_contents);
+    if (blocked_content_tab_helper &&
+        blocked_content_tab_helper->delegate()) {
+      content::WebContents* constraining_web_contents =
+          blocked_content_tab_helper->delegate()->
+              GetConstrainingWebContents(web_contents);
+      if (constraining_web_contents)
+        web_contents = constraining_web_contents;
+    }
+  }
+
+  Browser* browser =
+      web_contents ? chrome::FindBrowserWithWebContents(web_contents) : NULL;
+
+  // As a last resort, use the last active browser for this profile. Not ideal,
+  // but better than not showing the download at all.
+  if (browser == NULL) {
+    browser = chrome::FindLastActiveWithProfile(profile_,
+                                                chrome::GetActiveDesktop());
+  }
+
+  if (browser)
+    browser->ShowDownload(item);
+#endif
+}
+