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

chrome/browser/download/download_item.cc

Index: chrome/browser/download/download_item.cc
diff --git a/chrome/browser/download/download_item.cc b/chrome/browser/download/download_item.cc
index 52948f8e5c17113f37bb9b1c9d4a0cd8384f7634..1ae0927f2c72ef3811b1e469936e4836865c34b1 100644
--- a/chrome/browser/download/download_item.cc
+++ b/chrome/browser/download/download_item.cc
@@ -132,6 +132,7 @@ DownloadItem::DownloadItem(DownloadManager* download_manager,
       download_manager_(download_manager),
       is_paused_(false),
       open_when_complete_(false),
+      file_exists_(true),
       safety_state_(SAFE),
       danger_type_(NOT_DANGEROUS),
       auto_opened_(false),
@@ -172,6 +173,7 @@ DownloadItem::DownloadItem(DownloadManager* download_manager,
       download_manager_(download_manager),
       is_paused_(false),
       open_when_complete_(false),
+      file_exists_(true),
       safety_state_(GetSafetyState(info.is_dangerous_file,
                                    info.is_dangerous_url)),
       danger_type_(GetDangerType(info.is_dangerous_file,
@@ -211,6 +213,7 @@ DownloadItem::DownloadItem(DownloadManager* download_manager,
       download_manager_(download_manager),
       is_paused_(false),
       open_when_complete_(false),
+      file_exists_(true),
       safety_state_(SAFE),
       danger_type_(NOT_DANGEROUS),
       auto_opened_(false),
@@ -234,6 +237,10 @@ void DownloadItem::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 
+bool DownloadItem::HasObserver(Observer* observer) {
+  return observers_.HasObserver(observer);
+}
+
 void DownloadItem::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }