Detect removed files and reflect the state in chrome://downloads and the download shelf

chrome/browser/download/download_manager.cc

Index: chrome/browser/download/download_manager.cc
diff --git a/chrome/browser/download/download_manager.cc b/chrome/browser/download/download_manager.cc
index 6ef4a2b1e812ba36598d087e77f7925cacde2c3a..c47dacd055578477e6d120f810cb41fcd22afda3 100644
--- a/chrome/browser/download/download_manager.cc
+++ b/chrome/browser/download/download_manager.cc
@@ -265,6 +265,43 @@ void DownloadManager::StartDownload(DownloadCreateInfo* info) {
       info, NewCallback(this, &DownloadManager::CheckDownloadUrlDone));
 }
 
+void DownloadManager::CheckForFilesRemoval() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  for (DownloadMap::iterator it = history_downloads_.begin();
+       it != history_downloads_.end(); ++it) {
+    DownloadItem* download_item = it->second;
+    if (download_item->IsComplete() &&
+        !download_item->file_externally_removed()) {
+        BrowserThread::PostTask(
+            BrowserThread::FILE, FROM_HERE,
+            NewRunnableMethod(this,
+                &DownloadManager::CheckForFileRemovalOnFileThread,
+                it->first, download_item->GetTargetFilePath()));
+    }
+  }
+}
+
+void DownloadManager::CheckForFileRemovalOnFileThread(
+    int64 db_handle, const FilePath& path) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  if (!file_util::PathExists(path)) {
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        NewRunnableMethod(this,
+                          &DownloadManager::OnFileRemovalDetected,
+                          db_handle));
+  }
+}
+
+void DownloadManager::OnFileRemovalDetected(int64 db_handle) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DownloadMap::iterator it = history_downloads_.find(db_handle);
+  if (it != history_downloads_.end()) {
+    DownloadItem* download_item = it->second;
+    download_item->OnDownloadedFileRemoved();
+  }
+}
+
 void DownloadManager::CheckDownloadUrlDone(DownloadCreateInfo* info,
                                            bool is_dangerous_url) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));