Add "Show saved copy" button in dino page when there's offline copy

chrome/browser/net/net_error_tab_helper.cc

Index: chrome/browser/net/net_error_tab_helper.cc
diff --git a/chrome/browser/net/net_error_tab_helper.cc b/chrome/browser/net/net_error_tab_helper.cc
index a0e73cf6cb1e2c50084dc6ce1a1817860884b2fe..f800dcc98a95b58a5557b52a059a0661c808faa5 100644
--- a/chrome/browser/net/net_error_tab_helper.cc
+++ b/chrome/browser/net/net_error_tab_helper.cc
@@ -13,10 +13,13 @@
 #include "chrome/browser/net/net_error_diagnostics_dialog.h"
 #include "chrome/browser/platform_util.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/localized_error.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/render_messages.h"
 #include "components/error_page/common/net_error_info.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/navigation_entry.h"
+#include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/render_frame_host.h"
 #include "ipc/ipc_message_macros.h"
 #include "net/base/net_errors.h"
@@ -24,7 +27,7 @@
 
 #if defined(OS_ANDROID)
 #include "chrome/browser/android/tab_android.h"
-#endif
+#endif  // defined(OS_ANDROID)
 
 using content::BrowserContext;
 using content::BrowserThread;
@@ -124,8 +127,8 @@ void NetErrorTabHelper::DidStartProvisionalLoadForFrame(
   is_error_page_ = is_error_page;
 
 #if defined(OS_ANDROID)
-  SetHasOfflinePages(render_frame_host);
-#endif
+  SetOfflinePageInfo(render_frame_host);
+#endif  // defined(OS_ANDROID)
 }
 
 void NetErrorTabHelper::DidCommitProvisionalLoadForFrame(
@@ -177,7 +180,8 @@ bool NetErrorTabHelper::OnMessageReceived(
                         RunNetworkDiagnostics)
 #if defined(OS_ANDROID)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_ShowOfflinePages, ShowOfflinePages)
-#endif
+    IPC_MESSAGE_HANDLER(ChromeViewHostMsg_LoadOfflineCopy, LoadOfflineCopy)
+#endif  // defined(OS_ANDROID)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
 
@@ -286,23 +290,53 @@ void NetErrorTabHelper::RunNetworkDiagnosticsHelper(
 }
 
 #if defined(OS_ANDROID)
-void NetErrorTabHelper::SetHasOfflinePages(
-  content::RenderFrameHost* render_frame_host) {
+void NetErrorTabHelper::SetOfflinePageInfo(
+    content::RenderFrameHost* render_frame_host) {
   DCHECK(web_contents());
+  std::vector<GURL> offline_page_urls;
   TabAndroid* tab = TabAndroid::FromWebContents(web_contents());
-  bool has_offline_pages = tab && tab->HasOfflinePages();
+  if (tab)
+    tab->GetAllOfflinePageURLS(&offline_page_urls);
   render_frame_host->Send(
-      new ChromeViewMsg_SetHasOfflinePages(
-          render_frame_host->GetRoutingID(),
-          has_offline_pages));
+      new ChromeViewMsg_SetOfflinePageInfo(
+          render_frame_host->GetRoutingID(), offline_page_urls));
 }
 
 void NetErrorTabHelper::ShowOfflinePages() {
+  // Makes sure that this is coming from from an error page.
+  if (!IsFromErrorPage())
+    return;
+
   DCHECK(web_contents());
   TabAndroid* tab = TabAndroid::FromWebContents(web_contents());
   if (tab)
     tab->ShowOfflinePages();
 }
-#endif
+
+void NetErrorTabHelper::LoadOfflineCopy(const GURL& url) {
+  // Makes sure that this is coming from from an error page.
+  if (!IsFromErrorPage())
+    return;
+
+  GURL validated_url(url);
+  if (!validated_url.is_valid())
+    return;
+  DCHECK(web_contents());
+  if (validated_url != web_contents()->GetVisibleURL())

[nasko, 2015/11/19 15:11:41]

Why use GetVisibleURL? This is inconsistent with the check in IsFromErrorPage
and will lead to problems.

[mmenke, 2015/11/19 17:39:12]

I was concerned about allowing any page (Even one that's nominally an error
page) navigate to any cached url, both from a synchronization / racy navigation
messages standpoint, and from a random page telling us to navigate to random
cached pages standpoint, so I made this suggestion.

[nasko, 2015/11/19 17:52:53]

A page that has not committed should not be able to execute JS. If we want to be
defensive here, I'd suggest adding a BadMessageReceived() call and seeing if
this is ever hit. It will kill the renderer process and we can check for crash
reports caused by this condition.

[jianli, 2015/11/19 23:28:08]

We do not allow any page to navigate to any offline url. A page could only
access the offline copy of this page, not any other page. This is the reason we
send URL in the IPC. We've already been doing the validattion in
TabAndroid::LoadOfflineCopy. The extra check here is to just add another guard.
To address nasko's concern, should we just check against GetURL here?

+    return;
+
+  TabAndroid* tab = TabAndroid::FromWebContents(web_contents());
+  if (tab)
+    tab->LoadOfflineCopy(url);
+}
+
+bool NetErrorTabHelper::IsFromErrorPage() const {
+  content::NavigationEntry* entry =
+      web_contents()->GetController().GetLastCommittedEntry();
+  if (!entry)
+    return false;
+  return entry->GetPageType() == content::PAGE_TYPE_ERROR;
+}
+#endif  // defined(OS_ANDROID)
 
 }  // namespace chrome_browser_net