Offline Page Cache: do not save a snapshot of a page loaded from a snapshot.

chrome/browser/android/offline_pages/recent_tab_helper.cc

Index: chrome/browser/android/offline_pages/recent_tab_helper.cc
diff --git a/chrome/browser/android/offline_pages/recent_tab_helper.cc b/chrome/browser/android/offline_pages/recent_tab_helper.cc
index 9ab53f96fb4766b439c334d6857f8e4d5aed5d74..0f723c58a9a9d7da26da2e3ef043964b5c7cb5c8 100644
--- a/chrome/browser/android/offline_pages/recent_tab_helper.cc
+++ b/chrome/browser/android/offline_pages/recent_tab_helper.cc
@@ -164,7 +164,9 @@ void RecentTabHelper::DidFinishNavigation(
 
   // Check for conditions that would cause us not to snapshot.
   bool can_save = !navigation_handle->IsErrorPage() &&
-                  OfflinePageModel::CanSaveURL(snapshot_url_);
+                  OfflinePageModel::CanSaveURL(snapshot_url_) &&
+                  OfflinePageUtils::GetOfflinePageFromWebContents(
+                      web_contents()) == nullptr;
 
   UMA_HISTOGRAM_BOOLEAN("OfflinePages.CanSaveRecentPage", can_save);