[NTP::Downloads] Use last access time to filter old asset downloads.

content/public/test/fake_download_item.cc

Index: content/public/test/fake_download_item.cc
diff --git a/content/public/test/fake_download_item.cc b/content/public/test/fake_download_item.cc
index 6348c7ab84226dbf2d2f35212619023d21b64ef0..d9a333979dde71e0ac00d48818ac40dbba0d309d 100644
--- a/content/public/test/fake_download_item.cc
+++ b/content/public/test/fake_download_item.cc
@@ -142,6 +142,14 @@ int64_t FakeDownloadItem::GetReceivedBytes() const {
   return received_bytes_;
 }
 
+void FakeDownloadItem::SetLastAccessTime(base::Time time) {
+  last_access_time_ = time;
+}
+
+base::Time FakeDownloadItem::GetLastAccessTime() const {
+  return last_access_time_;
+}
+
 // The methods below are not supported and are not expected to be called.
 void FakeDownloadItem::ValidateDangerousDownload() {
   NOTREACHED();
@@ -370,11 +378,6 @@ bool FakeDownloadItem::GetOpened() const {
   return false;
 }
 
-base::Time FakeDownloadItem::GetLastAccessTime() const {
-  NOTREACHED();
-  return base::Time();
-}
-
 bool FakeDownloadItem::IsTransient() const {
   NOTREACHED();
   return false;
@@ -402,10 +405,6 @@ void FakeDownloadItem::SetOpened(bool opened) {
   NOTREACHED();
 }
 
-void FakeDownloadItem::SetLastAccessTime(base::Time time) {
-  NOTREACHED();
-}
-
 void FakeDownloadItem::SetDisplayName(const base::FilePath& name) {
   NOTREACHED();
 }